diff --git a/isaric/parsers/ccp-ghana.toml b/isaric/parsers/ccp-ghana.toml
index cbbd5d7..e5ffb26 100644
--- a/isaric/parsers/ccp-ghana.toml
+++ b/isaric/parsers/ccp-ghana.toml
@@ -33,6 +33,7 @@
       common = { visit_id = { field = "record_id", sensitive = true } }
 
 [adtl.defs]
+  checkbox = { values = { 1 = true } }
   "Y/N/NK" = { values = { 0 = false, 1 = true } }
   uid = { field = "record_id", sensitive = true }
 
@@ -620,8 +621,8 @@
   excludeWhen = "none"
   fields = [
     { field = "daily_antimal_cmyn", description = "Antimalarial agent?", ref = "Y/N/NK" },
-    { field = "daily_exper_cmtype___1", values = { 1 = true } },
-    { field = "daily_exper_cmtype___2", values = { 1 = true } },
+    { field = "daily_exper_cmtype___1", ref = "checkbox" },
+    { field = "daily_exper_cmtype___2", ref = "checkbox" },
   ]
 
 [visit.treatment_antimalarial_type]
@@ -715,7 +716,7 @@
   excludeWhen = "none"
   fields = [
     { field = "can_oxy_ther", description = "High-flow nasal canula oxygen therapy", ref = "Y/N/NK" },
-    { field = "overall_oxygen_cmtype___2", description = "Oxygen therapy interface: HF nasal cannula", ref = "Y/N/NK" },
+    { field = "overall_oxygen_cmtype___2", description = "Oxygen therapy interface: HF nasal cannula", ref = "checkbox" },
     { field = "daily_oxygen_cmtype_1", description = "Oxygen therapy interface: HF nasal cannula", ref = "Y/N/NK" },
   ]
 
@@ -799,27 +800,27 @@
   [[visit.treatment_oxygen_therapy.fields]]
     field = "overall_oxygen_cmtype___1"
     description = "Oxygen therapy?"
-    values = { 1 = true }
+    ref = "checkbox"
 
   [[visit.treatment_oxygen_therapy.fields]]
     field = "overall_oxygen_cmtype___2"
     description = "Oxygen therapy?"
-    values = { 1 = true }
+    ref = "checkbox"
 
   [[visit.treatment_oxygen_therapy.fields]]
     field = "overall_oxygen_cmtype___3"
     description = "Oxygen therapy?"
-    values = { 1 = true }
+    ref = "checkbox"
 
   [[visit.treatment_oxygen_therapy.fields]]
     field = "overall_oxygen_cmtype___4"
     description = "Oxygen therapy?"
-    values = { 1 = true }
+    ref = "checkbox"
 
   [[visit.treatment_oxygen_therapy.fields]]
     field = "overall_oxygen_cmtype___5"
     description = "Oxygen therapy?"
-    values = { 1 = true }
+    ref = "checkbox"
 
   [[visit.treatment_oxygen_therapy.fields]]
     field = "daily_oxygen_cmtype_1"
diff --git a/isaric/parsers/ccp-guinea.toml b/isaric/parsers/ccp-guinea.toml
index a06f308..a2ce24b 100644
--- a/isaric/parsers/ccp-guinea.toml
+++ b/isaric/parsers/ccp-guinea.toml
@@ -32,6 +32,7 @@
 
 [adtl.defs]
   "Y/N" = { values = { 1 = true, 2 = false } }
+  checkbox = { values = { 1 = true } }
 
   [adtl.defs.admissionDateHierarchy]
     combinedType = "firstNonNull"
@@ -552,8 +553,8 @@
   excludeWhen = "none"
   fields = [
     { field = "daily_antimal_cmyn", description = "Antimalarials?", values = { 1 = true, 0 = false } },
-    { field = "daily_exper_cmtype___1", values = { 1 = true } },
-    { field = "daily_exper_cmtype___2", values = { 1 = true } },
+    { field = "daily_exper_cmtype___1", ref = "checkbox" },
+    { field = "daily_exper_cmtype___2", ref = "checkbox" },
   ]
 
 [visit.treatment_antimalarial_type]
diff --git a/isaric/parsers/ccp-uganda-v2.toml b/isaric/parsers/ccp-uganda-v2.toml
index 17940e7..9609618 100644
--- a/isaric/parsers/ccp-uganda-v2.toml
+++ b/isaric/parsers/ccp-uganda-v2.toml
@@ -26,6 +26,9 @@
     1 = true
     0 = false
 
+  [adtl.defs.checkbox.values]
+    1 = true
+
 [adtl.defs.admissionDateHierarchy]
   combinedType = "firstNonNull"
   fields = [
@@ -598,7 +601,7 @@
     combinedType = "any"
     fields = [
       { field = "cof", ref = "Y/N" },
-      { field = "sick_symp___2", values = { 1 = true, 0 = false } },
+      { field = "sick_symp___2", ref = "checkbox" },
     ]
 
 [[observation]]
@@ -640,7 +643,7 @@
   ] } }
   duration_type = "event"
   phase = "admission"
-  is_present = { field = "sick_symp___3", values = { 1 = true, 0 = false } }
+  is_present = { field = "sick_symp___3", ref = "checkbox" }
 
 [[observation]]
   name = "diarrhoea"
@@ -674,7 +677,7 @@
   date = { field = "onset_date" }
   duration_type = "event"
   phase = "admission"
-  is_present = { field = "sick_symp___1", values = { 1 = true } }
+  is_present = { field = "sick_symp___1", ref = "checkbox" }
 
 [[observation]]
   name = "history_of_fever"
diff --git a/isaric/parsers/cocoa_pediatrics.toml b/isaric/parsers/cocoa_pediatrics.toml
index 0535be1..d96b5a4 100644
--- a/isaric/parsers/cocoa_pediatrics.toml
+++ b/isaric/parsers/cocoa_pediatrics.toml
@@ -24,6 +24,7 @@
 
 [adtl.defs]
   "Y/N/NK" = { values = { 0 = false, 1 = true } }
+  checkbox = { values = { 1 = true } }
 
   [adtl.defs.admissionDateHierarchy]
     combinedType = "firstNonNull"
@@ -376,7 +377,7 @@
   name = "cough"
   phase = "followup"
   date = { field = "date" }
-  is_present = { field = "ongoing_symptoms___2", values = { 1 = true } }
+  is_present = { field = "ongoing_symptoms___2", ref = "checkbox" }
 
 [[observation]]
   name = "cough_dry"
@@ -414,7 +415,7 @@
   name = "diarrhoea"
   phase = "followup"
   date = { field = "date" }
-  is_present = { field = "ongoing_symptoms___10", values = { 1 = true } }
+  is_present = { field = "ongoing_symptoms___10", ref = "checkbox" }
 
 [[observation]]
   name = "diastolic_blood_pressure_mmHg"
@@ -440,7 +441,7 @@
   name = "hepatomegaly"
   phase = "admission"
   date = { field = "hostdat" }
-  is_present = { field = "cardiac_failure___4", values = { 1 = true } }
+  is_present = { field = "cardiac_failure___4", ref = "checkbox" }
 
 [[observation]]
   name = "history_of_fever"
@@ -454,7 +455,7 @@
   name = "history_of_fever"
   phase = "followup"
   date = { field = "date" }
-  is_present = { field = "ongoing_symptoms___1", values = { 1 = true } }
+  is_present = { field = "ongoing_symptoms___1", ref = "checkbox" }
 
 [[observation]]
   name = "fatigue_malaise"
@@ -480,7 +481,7 @@
   name = "feeding_intolerance_pediatrics"
   phase = "followup"
   date = { field = "date" }
-  is_present = { field = "ongoing_symptoms___11", values = { 1 = true } }
+  is_present = { field = "ongoing_symptoms___11", ref = "checkbox" }
 
 [[observation]]
   name = "inability_to_walk"
@@ -556,8 +557,8 @@
     combinedType = "any"
     excludeWhen = "none"
     fields = [
-      { field = "myalgia_ceoccur_v2", values = { 1 = true } },
-      { field = "jointpain_ceoccur_v2", values = { 1 = true } },
+      { field = "myalgia_ceoccur_v2", ref = "checkbox" },
+      { field = "jointpain_ceoccur_v2", ref = "checkbox" },
     ]
 
 [[observation]]
@@ -660,7 +661,7 @@
   name = "shortness_of_breath"
   phase = "followup"
   date = { field = "date" }
-  is_present = { field = "ongoing_symptoms___3", values = { 1 = true } }
+  is_present = { field = "ongoing_symptoms___3", ref = "checkbox" }
 
 [[observation]]
   name = "skin_rash"
@@ -674,7 +675,7 @@
   name = "skin_rash"
   phase = "followup"
   date = { field = "date" }
-  is_present = { field = "ongoing_symptoms___5", values = { 1 = true } }
+  is_present = { field = "ongoing_symptoms___5", ref = "checkbox" }
 
 [[observation]]
   name = "skin_ulcers"
@@ -740,7 +741,7 @@
   name = "vomiting_nausea"
   phase = "followup"
   date = { field = "date" }
-  is_present = { field = "ongoing_symptoms___9", values = { 1 = true } }
+  is_present = { field = "ongoing_symptoms___9", ref = "checkbox" }
 
 [[observation]]
   name = "blantyre_coma_score"
diff --git a/isaric/parsers/datcov-southafrica.toml b/isaric/parsers/datcov-southafrica.toml
index 65b4cd4..70040cd 100644
--- a/isaric/parsers/datcov-southafrica.toml
+++ b/isaric/parsers/datcov-southafrica.toml
@@ -22,6 +22,9 @@
     1 = true
     0 = false
 
+  [adtl.defs.checkbox.values]
+    1 = true
+
 [adtl.defs.subjectId]
   combinedType = "firstNonNull"
   fields = [{ field = "PatientId" }, { field = "NICDCaseID" }]
@@ -135,35 +138,35 @@
   [subject.has_chronic_hematologic_disease]
     field = "flw_ongoing_chronic_list___12"
     description = "Diagnosed, ongoing condition before COVID-19 diagnosis: Blood disorder"
-    ref = "Y/N/NK"
+    ref = "checkbox"
 
   [subject.has_asplenia]
     field = "flw_ongoing_chronic_list___10"
-    ref = "Y/N/NK"
+    ref = "checkbox"
     description = "Asplenia"
 
   [subject.has_tuberculosis]
     combinedType = "any"
     fields = [
       { field = "Tuberculosis Active", values = { 'Yes' = true, 'No' = false } }, # values = ['No', 'Unknown', 'Yes', 'UNKNOWN', nan]
-      { field = "flw_ongoing_chronic_list___20", ref = "Y/N/NK" },
+      { field = "flw_ongoing_chronic_list___20", ref = "checkbox" },
     ]
 
   [subject.has_dementia]
     field = "flw_ongoing_chronic_list___15"
-    ref = "Y/N/NK"
+    ref = "checkbox"
     description = "Dementia"
 
   [subject.has_rheumatologic_disorder]
     field = "flw_ongoing_chronic_list___13"
-    ref = "Y/N/NK"
+    ref = "checkbox"
     description = "Rhemumatologic disorder"
 
   [subject.has_hiv]
     combinedType = "any"
     fields = [
       { field = "HIV Positive", values = { 'Yes' = true, 'No' = false } }, # values = ['No', 'Unknown', 'Yes', nan]}
-      { field = "flw_ongoing_chronic_list___16", ref = "Y/N/NK" },
+      { field = "flw_ongoing_chronic_list___16", ref = "checkbox" },
     ]
 
   [subject.has_obesity]
@@ -175,14 +178,14 @@
     combinedType = "any"
     fields = [
       { field = "Hypertension", values = { 'Yes' = true, 'No' = false } },
-      { field = "flw_ongoing_chronic_list___2", ref = "Y/N/NK" },
+      { field = "flw_ongoing_chronic_list___2", ref = "checkbox" },
     ]
 
   [subject.has_malignant_neoplasm]
     combinedType = "any"
     fields = [
       { field = "Malignancy", values = { 'Yes' = true, 'No' = false } }, # values = ['No', 'Unknown', 'UNKNOWN', 'Yes', nan]
-      { field = "flw_ongoing_chronic_list___11", ref = "Y/N/NK" },
+      { field = "flw_ongoing_chronic_list___11", ref = "checkbox" },
     ]
 
   [subject.has_smoking]
@@ -196,30 +199,30 @@
     combinedType = "any"
     fields = [
       { field = "Asthma", values = { 'Yes' = true, 'No' = false } }, # values = ['No', 'Unknown', 'Yes', 'UNKNOWN', nan]
-      { field = "flw_ongoing_chronic_list___3", ref = "Y/N/NK" },
+      { field = "flw_ongoing_chronic_list___3", ref = "checkbox" },
     ]
 
   [subject.has_chronic_cardiac_disease]
     combinedType = "any"
     fields = [
       { field = "Cardiac Disease", values = { 'Yes' = true, 'No' = false } }, # values = ['No', 'Unknown', 'UNKNOWN', 'Yes', nan]
-      { field = "flw_ongoing_chronic_list___1", ref = "Y/N/NK" },
+      { field = "flw_ongoing_chronic_list___1", ref = "checkbox" },
     ]
 
   [subject.has_chronic_kidney_disease]
     combinedType = "any"
     fields = [
       { field = "Chronic Renal Failure", values = { 'Yes' = true, 'No' = false } }, # values = ['No', 'Unknown', 'UNKNOWN', 'Yes', nan] }
-      { field = "flw_ongoing_chronic_list___8", ref = "Y/N/NK" },
+      { field = "flw_ongoing_chronic_list___8", ref = "checkbox" },
     ]
 
   [subject.has_diabetes]
     combinedType = "any"
     fields = [
-      { field = "Diabetes", values = { 'Yes' = true, 'No' = false } },                                  # values = ['No', 'Unknown', 'Yes', 'UNKNOWN', nan]
-      { field = "flw_ongoing_chronic_list___5", ref = "Y/N/NK", description = "Diabetes Type 1" },
-      { field = "flw_ongoing_chronic_list___6", ref = "Y/N/NK", description = "Diabetes Type 2" },
-      { field = "flw_ongoing_chronic_list___7", ref = "Y/N/NK", description = "Diabetes Gestational" },
+      { field = "Diabetes", values = { 'Yes' = true, 'No' = false } },                                    # values = ['No', 'Unknown', 'Yes', 'UNKNOWN', nan]
+      { field = "flw_ongoing_chronic_list___5", ref = "checkbox", description = "Diabetes Type 1" },
+      { field = "flw_ongoing_chronic_list___6", ref = "checkbox", description = "Diabetes Type 2" },
+      { field = "flw_ongoing_chronic_list___7", ref = "checkbox", description = "Diabetes Gestational" },
     ]
     # can we assume diabetes as a disease was there before COVID? and so the followup data applies here?
 
@@ -233,14 +236,9 @@
 
   [subject.has_liver_disease]
     field = "flw_ongoing_chronic_list___9"
-    ref = "Y/N/NK"
+    ref = "checkbox"
     description = "Liver disease"
 
-    # [subject.has_hiv_viral_suppression]
-    #   field = "HIV Viral Suppression"
-    #   values = { 'Yes' = true, 'No' = false }
-    #   # values = [nan, 'No', 'Unknown', 'Yes']
-
   [subject.has_tuberculosis_past]
     field = "Tuberculosis Past"
     values = { 'Yes' = true, 'No' = false }
diff --git a/isaric/parsers/isaric-ccpuk.toml b/isaric/parsers/isaric-ccpuk.toml
index 8a2cfae..16e7f8c 100644
--- a/isaric/parsers/isaric-ccpuk.toml
+++ b/isaric/parsers/isaric-ccpuk.toml
@@ -13,6 +13,9 @@
     1 = true
     2 = false
 
+  [adtl.defs.checkbox.values]
+    1 = true
+
 [adtl.defs.admissionDateHierarchy]
   combinedType = "firstNonNull"
   fields = [
@@ -445,7 +448,7 @@
 
   [visit.treatment_antimalarial]
     field = "antiviral_cmtrt___7"
-    values = { 1 = true }
+    ref = "checkbox"
 
   [visit.treatment_antimalarial_type]
     combinedType = "set"
diff --git a/isaric/parsers/isaric-rapid.toml b/isaric/parsers/isaric-rapid.toml
index 44b554e..adff30b 100644
--- a/isaric/parsers/isaric-rapid.toml
+++ b/isaric/parsers/isaric-rapid.toml
@@ -627,14 +627,14 @@
     { field = "overall_antimal_cmyn", ref = "Y/N/NK", description = "Antimalarial agent?" },
     { field = "daily_antimal_cmyn", ref = "Y/N/NK", description = "Antimalarial agent?" },
     { field = "antimal_cmyn", ref = "Y/N/NK", description = "Antimalarial agent on the first day of admission?" },
-    { fieldPattern = ".*exper_cmtype___1", values = { 1 = true } },
-    { fieldPattern = ".*exper_cmtype___2", values = { 1 = true } },
-    { fieldPattern = ".*antimal_cmtype___1", values = { 1 = true } },
-    { fieldPattern = ".*antimal_cmtype___2", values = { 1 = true } },
-    { fieldPattern = ".*antimal_cmtype___3", values = { 1 = true } },
-    { fieldPattern = ".*antimal_cmtype___4", values = { 1 = true } },
-    { fieldPattern = ".*antimal_cmtype___5", values = { 1 = true } },
-    { fieldPattern = ".*antimal_cmtype___6", values = { 1 = true } },
+    { fieldPattern = ".*exper_cmtype___1", ref = "checkbox" },
+    { fieldPattern = ".*exper_cmtype___2", ref = "checkbox" },
+    { fieldPattern = ".*antimal_cmtype___1", ref = "checkbox" },
+    { fieldPattern = ".*antimal_cmtype___2", ref = "checkbox" },
+    { fieldPattern = ".*antimal_cmtype___3", ref = "checkbox" },
+    { fieldPattern = ".*antimal_cmtype___4", ref = "checkbox" },
+    { fieldPattern = ".*antimal_cmtype___5", ref = "checkbox" },
+    { fieldPattern = ".*antimal_cmtype___6", ref = "checkbox" },
   ]
 
 [visit.treatment_antimalarial_type]
@@ -659,7 +659,7 @@
     { field = "overall_antiviral_cmyn", ref = "Y/N/NK", description = "Antiviral agent?" },
     { field = "daily_antiviral_cmyn", ref = "Y/N/NK", description = "Antiviral agent?" },
     { field = "antiviral_cmyn", ref = "Y/N/NK", description = "Antiviral agent on the first day of admission?" },
-    { fieldPattern = ".*exper_cmtype___3", values = { 1 = true } },
+    { fieldPattern = ".*exper_cmtype___3", ref = "checkbox" },
   ]
 
 [visit.treatment_antiviral_type]
@@ -866,7 +866,7 @@
     { fieldPattern = ".*oxygen_cmoccur", ref = "Y/N/NK", description = "Oxygen therepy?" },
     { field = "ccm_a_fi02_lbyn", ref = "Y/N/NK", description = "Any supplemental oxygen?" },
     { field = "ccm_b_hhfnc_prtrt", ref = "Y/N/NK", description = "Humidified high flow nasal cannula (HHFNC)?" },
-    { fieldPattern = "overall_oxygen_cmtype.*", values = { 1 = true }, description = "Oxygen therapy? (interface)" },
+    { fieldPattern = "overall_oxygen_cmtype.*", ref = "checkbox", description = "Oxygen therapy? (interface)" },
     { fieldPattern = ".*oxygen_cmtype", values = { 1 = true, 2 = true, 3 = true, 4 = true }, description = "Oxygen therapy? (interface)" },
     { fieldPattern = ".*invasive_proccur", ref = "Y/N/NK", description = "Invasive ventilation?" },
     { field = "ccm_b_invasive_prtrt", ref = "Y/N/NK", description = "Invasive ventilation?" },
@@ -902,7 +902,7 @@
   excludeWhen = "none"
   fields = [
     { field = "ccm_b_hhfnc_prtrt", ref = "Y/N/NK", description = "Humidified high flow nasal cannula (HHFNC)?" },
-    { field = "overall_oxygen_cmtype___2", values = { 1 = true }, description = "Oxygen therapy? (interface)" },
+    { field = "overall_oxygen_cmtype___2", ref = "checkbox", description = "Oxygen therapy? (interface)" },
     { field = "daily_oxygen_cmtype", values = { 2 = true }, description = "Oxygen therapy? (interface)" },
     { field = "oxygen_cmtype", values = { 2 = true }, description = "Oxygen therapy? (interface)" },
   ]
@@ -910,9 +910,9 @@
 [visit.treatment_oxygen_mask_prongs]
   combinedType = "any"
   fields = [
-    { field = "overall_oxygen_cmtype___1", values = { 1 = true }, description = "Nasal prongs" },
-    { field = "overall_oxygen_cmtype___3", values = { 1 = true }, description = "Mask" },
-    { field = "overall_oxygen_cmtype___4", values = { 1 = true }, description = "Mask with reservoir" },
+    { field = "overall_oxygen_cmtype___1", ref = "checkbox", description = "Nasal prongs" },
+    { field = "overall_oxygen_cmtype___3", ref = "checkbox", description = "Mask" },
+    { field = "overall_oxygen_cmtype___4", ref = "checkbox", description = "Mask with reservoir" },
     { field = "oxygen_cmtype", values = { 1 = true, 3 = true, 4 = true }, description = "Oxygen therapy? (interface)" },
     { field = "daily_oxygen_cmtype", values = { 1 = true, 3 = true, 4 = true }, description = "Oxygen therapy? (interface)" },
   ]
diff --git a/isaric/parsers/isaric_washington.toml b/isaric/parsers/isaric_washington.toml
index 666686f..a45b8b3 100644
--- a/isaric/parsers/isaric_washington.toml
+++ b/isaric/parsers/isaric_washington.toml
@@ -24,6 +24,7 @@
 
 [adtl.defs]
   "Y/N" = { values = { 0 = false, 1 = true } }
+  checkbox = { values = { 1 = true } }
 
   [adtl.defs.countryMap.values]
     1 = "USA"
@@ -97,30 +98,30 @@
 
   [subject.has_tuberculosis]
     field = "any_other_pos___4"
-    values = { 1 = true }
+    ref = "checkbox"
 
   [subject.has_dementia]
     field = "comorbidities___34"
-    values = { 1 = true }
+    ref = "checkbox"
 
   [subject.has_obesity]
     field = "comorbidities___30"
-    values = { 1 = true }
+    ref = "checkbox"
 
   [subject.has_hiv]
     combinedType = "any"
     fields = [
-      { field = "comorbidities___22", values = { 1 = true } },
-      { field = "any_other_pos___1", values = { 1 = true } },
+      { field = "comorbidities___22", ref = "checkbox" },
+      { field = "any_other_pos___1", ref = "checkbox" },
     ]
 
   [subject.has_hypertension]
     field = "comorbidities___3"
-    values = { 1 = true }
+    ref = "checkbox"
 
   [subject.has_malignant_neoplasm]
     field = "comorbidities___20"
-    values = { 1 = true }
+    ref = "checkbox"
 
   [subject.has_smoking]
     combinedType = "firstNonNull"
@@ -132,40 +133,40 @@
 
   [subject.has_asthma]
     field = "comorbidities___8"
-    values = { 1 = true }
+    ref = "checkbox"
 
   [subject.has_chronic_kidney_disease]
     field = "comorbidities___10"
-    values = { 1 = true }
+    ref = "checkbox"
 
   [subject.has_chronic_cardiac_disease]
     combinedType = "any"
     fields = [
-      { field = "comorbidities___2", values = { 1 = true }, description = "Coronary artery disease" },
-      { field = "comorbidities___4", values = { 1 = true }, description = "Cardiac arrhythmia" },
-      { field = "comorbidities___5", values = { 1 = true }, description = "Congestive heart failure" },
-      { field = "comorbidities___6", values = { 1 = true }, description = "Valvular heart disease" },
+      { field = "comorbidities___2", ref = "checkbox", description = "Coronary artery disease" },
+      { field = "comorbidities___4", ref = "checkbox", description = "Cardiac arrhythmia" },
+      { field = "comorbidities___5", ref = "checkbox", description = "Congestive heart failure" },
+      { field = "comorbidities___6", ref = "checkbox", description = "Valvular heart disease" },
     ]
 
   [subject.has_chronic_respiratory_disease]
     combinedType = "any"
     fields = [
-      { field = "comorbidities___7", values = { 1 = true } },
-      { field = "comorbidities___9", values = { 1 = true } },
+      { field = "comorbidities___7", ref = "checkbox" },
+      { field = "comorbidities___9", ref = "checkbox" },
     ]
 
   [subject.has_chronic_hematologic_disease]
     field = "comorbidities___19"
-    values = { 1 = true }
+    ref = "checkbox"
     description = "hematologic malignancy"
 
   [subject.has_rheumatologic_disorder]
     field = "comorbidities___25"
-    values = { 1 = true }
+    ref = "checkbox"
 
   [subject.has_diabetes]
     field = "comorbidities___12"
-    values = { 1 = true }
+    ref = "checkbox"
 
   [subject.diabetes_type]
     combinedType = "firstNonNull"
@@ -178,27 +179,27 @@
   [subject.has_liver_disease]
     combinedType = "any"
     fields = [
-      { field = "comorbidities___14", values = { 1 = true } },
-      { field = "comorbidities___15", values = { 1 = true }, description = "Hep B" },
-      { field = "comorbidities___16", values = { 1 = true }, description = "Hep C" },
+      { field = "comorbidities___14", ref = "checkbox" },
+      { field = "comorbidities___15", ref = "checkbox", description = "Hep B" },
+      { field = "comorbidities___16", ref = "checkbox", description = "Hep C" },
     ]
 
 
   [subject.has_malnutrition]
     field = "comorbidities___29"
-    values = { 1 = true }
+    ref = "checkbox"
 
   [subject.has_solid_organ_transplant]
     field = "comorbidities___21"
-    values = { 1 = true }
+    ref = "checkbox"
 
   [subject.has_hiv_art]
     field = "pre_hospital_medication___3"
-    values = { 1 = true }
+    ref = "checkbox"
 
   [subject.has_immunosuppression]
     field = "comorbidities___22"
-    values = { 1 = true }
+    ref = "checkbox"
 
   [subject.has_comorbidity_other]
     combinedType = "set"
@@ -220,8 +221,8 @@
   [subject.icu_admitted]
     combinedType = "any"
     fields = [
-      { field = "admitted_to_icu", values = { 1 = true } },
-      { field = "is_patient_admitted_to_icu", values = { 1 = true } },
+      { field = "admitted_to_icu", ref = "checkbox" },
+      { field = "is_patient_admitted_to_icu", ref = "checkbox" },
     ]
 
 
@@ -247,8 +248,8 @@
   [visit.icu_admission]
     combinedType = "any"
     fields = [
-      { field = "admitted_to_icu", values = { 1 = true } },
-      { field = "is_patient_admitted_to_icu", values = { 1 = true } },
+      { field = "admitted_to_icu", ref = "checkbox" },
+      { field = "is_patient_admitted_to_icu", ref = "checkbox" },
     ]
 
   [visit.icu_admission_dates]
@@ -266,95 +267,95 @@
 
   [visit.treatment_inotropes_vasopressors]
     field = "icu_level_care___3"
-    values = { 1 = true }
+    ref = "checkbox"
 
   [visit.treatment_ecmo]
     combinedType = "any"
     fields = [
-      { field = "treatment_events___5", values = { 1 = true } },
-      { field = "oxygenation_methods_2___6", values = { 1 = true } },
+      { field = "treatment_events___5", ref = "checkbox" },
+      { field = "oxygenation_methods_2___6", ref = "checkbox" },
     ]
 
   [visit.treatment_oxygen_therapy]
     combinedType = "any"
     excludeWhen = "none"
     fields = [
-      { field = "oxygenation_methods_2___1", values = { 1 = true }, description = "invasive" },
-      { field = "oxygenation_methods_2___2", values = { 1 = true }, description = "non-invasive" },
-      { field = "oxygenation_methods_2___3", values = { 1 = true }, description = "HFNC" },
-      { field = "oxygenation_methods_2___4", values = { 1 = true }, description = "face mask" },
-      { field = "oxygenation_methods_2___6", values = { 1 = true }, description = "ecmo" },
-      { field = "oxygenation_methods_2___7", values = { 1 = true }, description = "nasal cannula" },
-      { field = "icu_level_care___1", values = { 1 = true }, description = "HFNC" },
-      { field = "icu_level_care___4", values = { 1 = true }, description = "mechanical ventilation" },
-      { field = "icu_level_care___5", values = { 1 = true }, description = "non-invasive +ve pressure ventilation" },
-      { field = "icu_level_care___8", values = { 1 = true }, description = "prone ventilation" },
-      { field = "treatment_events___1", values = { 1 = true }, description = "prone ventilation" },
-      { field = "treatment_events___5", values = { 1 = true }, description = "extracorporeal support (ecmo)" },
+      { field = "oxygenation_methods_2___1", ref = "checkbox", description = "invasive" },
+      { field = "oxygenation_methods_2___2", ref = "checkbox", description = "non-invasive" },
+      { field = "oxygenation_methods_2___3", ref = "checkbox", description = "HFNC" },
+      { field = "oxygenation_methods_2___4", ref = "checkbox", description = "face mask" },
+      { field = "oxygenation_methods_2___6", ref = "checkbox", description = "ecmo" },
+      { field = "oxygenation_methods_2___7", ref = "checkbox", description = "nasal cannula" },
+      { field = "icu_level_care___1", ref = "checkbox", description = "HFNC" },
+      { field = "icu_level_care___4", ref = "checkbox", description = "mechanical ventilation" },
+      { field = "icu_level_care___5", ref = "checkbox", description = "non-invasive +ve pressure ventilation" },
+      { field = "icu_level_care___8", ref = "checkbox", description = "prone ventilation" },
+      { field = "treatment_events___1", ref = "checkbox", description = "prone ventilation" },
+      { field = "treatment_events___5", ref = "checkbox", description = "extracorporeal support (ecmo)" },
     ]
 
   [visit.treatment_oxygen_mask_prongs]
     combinedType = "any"
     fields = [
-      { field = "oxygenation_methods_2___4", values = { 1 = true }, description = "face mask" },
-      { field = "oxygenation_methods_2___7", values = { 1 = true }, description = "nasal cannula" },
+      { field = "oxygenation_methods_2___4", ref = "checkbox", description = "face mask" },
+      { field = "oxygenation_methods_2___7", ref = "checkbox", description = "nasal cannula" },
     ]
 
   [visit.treatment_prone_position]
     combinedType = "any"
     fields = [
-      { field = "treatment_events___1", values = { 1 = true } },
-      { field = "oxygenation_methods_2___5", values = { 1 = true }, description = "proning" },
-      { field = "icu_level_care___8", values = { 1 = true }, description = "prone ventilation" },
-      { field = "icu_level_care___11", values = { 1 = true }, description = "self-proning not on ventilator" },
+      { field = "treatment_events___1", ref = "checkbox" },
+      { field = "oxygenation_methods_2___5", ref = "checkbox", description = "proning" },
+      { field = "icu_level_care___8", ref = "checkbox", description = "prone ventilation" },
+      { field = "icu_level_care___11", ref = "checkbox", description = "self-proning not on ventilator" },
     ]
 
 
   [visit.treatment_invasive_ventilation]
     combinedType = "any"
     fields = [
-      { field = "icu_level_care___4", values = { 1 = true } },
-      { field = "oxygenation_methods_2___1", values = { 1 = true } },
+      { field = "icu_level_care___4", ref = "checkbox" },
+      { field = "oxygenation_methods_2___1", ref = "checkbox" },
     ]
 
   [visit.treatment_inhaled_nitric_oxide]
     combinedType = "any"
     fields = [
-      { field = "treatment_events___2", values = { 1 = true } },
-      { field = "icu_level_care___9", values = { 1 = true } },
+      { field = "treatment_events___2", ref = "checkbox" },
+      { field = "icu_level_care___9", ref = "checkbox" },
     ]
 
   [visit.treatment_noninvasive_ventilation]
     combinedType = "any"
     fields = [
-      { field = "icu_level_care___5", values = { 1 = true } },
-      { field = "oxygenation_methods_2___2", values = { 1 = true } },
+      { field = "icu_level_care___5", ref = "checkbox" },
+      { field = "oxygenation_methods_2___2", ref = "checkbox" },
     ]
 
   [visit.treatment_high_flow_nasal_cannula]
     combinedType = "any"
     fields = [
-      { field = "icu_level_care___1", values = { 1 = true } },
-      { field = "oxygenation_methods_2___3", values = { 1 = true } },
+      { field = "icu_level_care___1", ref = "checkbox" },
+      { field = "oxygenation_methods_2___3", ref = "checkbox" },
     ]
 
   [visit.treatment_neuromuscular_blocking_agents]
     combinedType = "any"
-    fields = [{ field = "icu_level_care___7", values = { 1 = true } }]
+    fields = [{ field = "icu_level_care___7", ref = "checkbox" }]
 
   [visit.treatment_dialysis]
     combinedType = "any"
     fields = [
       { field = "crrt_duration", apply = { function = "isNotNull" } },
-      { field = "icu_level_care___2", values = { 1 = true } },
+      { field = "icu_level_care___2", ref = "checkbox" },
     ]
 
   [visit.treatment_cardiovascular_support]
     combinedType = "any"
     fields = [
-      { field = "treatment_events___5", values = { 1 = true } },
-      { field = "oxygenation_methods_2___6", values = { 1 = true } },
-      { field = "icu_level_care___3", values = { 1 = true } },
+      { field = "treatment_events___5", ref = "checkbox" },
+      { field = "oxygenation_methods_2___6", ref = "checkbox" },
+      { field = "icu_level_care___3", ref = "checkbox" },
     ]
 
   [visit.outcome]
@@ -371,31 +372,31 @@
   name = "abdominal_pain"
   date = { field = "ADMIT DATE" }
   phase = "admission"
-  is_present = { field = "signs_and_symptoms_at_hosp___1", values = { 1 = true } }
+  is_present = { field = "signs_and_symptoms_at_hosp___1", ref = "checkbox" }
 
 [[observation]]
   name = "confusion"
   date = { field = "ADMIT DATE" }
   phase = "admission"
-  is_present = { field = "signs_and_symptoms_at_hosp___8", values = { 1 = true } }
+  is_present = { field = "signs_and_symptoms_at_hosp___8", ref = "checkbox" }
 
 [[observation]]
   name = "anorexia"
   date = { field = "ADMIT DATE" }
   phase = "admission"
-  is_present = { field = "signs_and_symptoms_at_hosp___3", values = { 1 = true } }
+  is_present = { field = "signs_and_symptoms_at_hosp___3", ref = "checkbox" }
 
 [[observation]]
   name = "chest_pain"
   date = { field = "ADMIT DATE" }
   phase = "admission"
-  is_present = { field = "signs_and_symptoms_at_hosp___6", values = { 1 = true } }
+  is_present = { field = "signs_and_symptoms_at_hosp___6", ref = "checkbox" }
 
 [[observation]]
   name = "conjunctivitis"
   date = { field = "ADMIT DATE" }
   phase = "admission"
-  is_present = { field = "signs_and_symptoms_at_hosp___9", values = { 1 = true } }
+  is_present = { field = "signs_and_symptoms_at_hosp___9", ref = "checkbox" }
 
 [[observation]]
   name = "cough"
@@ -405,46 +406,46 @@
   [observation.is_present]
     combinedType = "any"
     fields = [
-      { field = "signs_and_symptoms_at_hosp___10", values = { 1 = true } },
-      { field = "signs_and_symptoms_at_hosp___11", values = { 1 = true } },
-      { field = "signs_and_symptoms_at_hosp___17", values = { 1 = true } },
+      { field = "signs_and_symptoms_at_hosp___10", ref = "checkbox" },
+      { field = "signs_and_symptoms_at_hosp___11", ref = "checkbox" },
+      { field = "signs_and_symptoms_at_hosp___17", ref = "checkbox" },
     ]
 
 [[observation]]
   name = "cough_dry"
   date = { field = "ADMIT DATE" }
   phase = "admission"
-  is_present = { field = "signs_and_symptoms_at_hosp___10", values = { 1 = true } }
+  is_present = { field = "signs_and_symptoms_at_hosp___10", ref = "checkbox" }
 
 [[observation]]
   name = "cough_with_sputum_production"
   date = { field = "ADMIT DATE" }
   phase = "admission"
-  is_present = { field = "signs_and_symptoms_at_hosp___11", values = { 1 = true } }
+  is_present = { field = "signs_and_symptoms_at_hosp___11", ref = "checkbox" }
 
 [[observation]]
   name = "cough_with_haemoptysis"
   date = { field = "ADMIT DATE" }
   phase = "admission"
-  is_present = { field = "signs_and_symptoms_at_hosp___17", values = { 1 = true } }
+  is_present = { field = "signs_and_symptoms_at_hosp___17", ref = "checkbox" }
 
 [[observation]]
   name = "diarrhoea"
   date = { field = "ADMIT DATE" }
   phase = "admission"
-  is_present = { field = "signs_and_symptoms_at_hosp___12", values = { 1 = true } }
+  is_present = { field = "signs_and_symptoms_at_hosp___12", ref = "checkbox" }
 
 [[observation]]
   name = "fatigue_malaise"
   date = { field = "ADMIT DATE" }
   phase = "admission"
-  is_present = { field = "signs_and_symptoms_at_hosp___18", values = { 1 = true } }
+  is_present = { field = "signs_and_symptoms_at_hosp___18", ref = "checkbox" }
 
 [[observation]]
   name = "headache"
   date = { field = "ADMIT DATE" }
   phase = "admission"
-  is_present = { field = "signs_and_symptoms_at_hosp___16", values = { 1 = true } }
+  is_present = { field = "signs_and_symptoms_at_hosp___16", ref = "checkbox" }
 
 [[observation]]
   name = "hepatomegaly"
@@ -454,37 +455,37 @@
   ] } }
   duration_type = "event"
   phase = "study"
-  is_present = { field = "complications___19", values = { 1 = true } }
+  is_present = { field = "complications___19", ref = "checkbox" }
 
 [[observation]]
   name = "history_of_fever"
   date = { field = "ADMIT DATE" }
   phase = "admission"
-  is_present = { field = "signs_and_symptoms_at_hosp___15", values = { 1 = true } }
+  is_present = { field = "signs_and_symptoms_at_hosp___15", ref = "checkbox" }
 
 [[observation]]
   name = "joint_pain"
   date = { field = "ADMIT DATE" }
   phase = "admission"
-  is_present = { field = "signs_and_symptoms_at_hosp___5", values = { 1 = true } }
+  is_present = { field = "signs_and_symptoms_at_hosp___5", ref = "checkbox" }
 
 [[observation]]
   name = "musculoskeletal_pain"
   date = { field = "ADMIT DATE" }
   phase = "admission"
-  is_present = { field = "signs_and_symptoms_at_hosp___5", values = { 1 = true } }
+  is_present = { field = "signs_and_symptoms_at_hosp___5", ref = "checkbox" }
 
 [[observation]]
   name = "loss_of_smell"
   date = { field = "ADMIT DATE" }
   phase = "admission"
-  is_present = { field = "signs_and_symptoms_at_hosp___4", values = { 1 = true } }
+  is_present = { field = "signs_and_symptoms_at_hosp___4", ref = "checkbox" }
 
 [[observation]]
   name = "loss_of_taste"
   date = { field = "ADMIT DATE" }
   phase = "admission"
-  is_present = { field = "signs_and_symptoms_at_hosp___2", values = { 1 = true } }
+  is_present = { field = "signs_and_symptoms_at_hosp___2", ref = "checkbox" }
 
 [[observation]]
   name = "loss_of_smell_or_taste"
@@ -494,51 +495,51 @@
   [observation.is_present]
     combinedType = "any"
     fields = [
-      { field = "signs_and_symptoms_at_hosp___4", values = { 1 = true } },
-      { field = "signs_and_symptoms_at_hosp___2", values = { 1 = true } },
+      { field = "signs_and_symptoms_at_hosp___4", ref = "checkbox" },
+      { field = "signs_and_symptoms_at_hosp___2", ref = "checkbox" },
     ]
 
 [[observation]]
   name = "lymphadenopathy"
   date = { field = "ADMIT DATE" }
   phase = "admission"
-  is_present = { field = "signs_and_symptoms_at_hosp___27", values = { 1 = true } }
+  is_present = { field = "signs_and_symptoms_at_hosp___27", ref = "checkbox" }
 
 [[observation]]
   name = "seizures"
   date = { field = "ADMIT DATE" }
   phase = "admission"
-  is_present = { field = "signs_and_symptoms_at_hosp___23", values = { 1 = true } }
+  is_present = { field = "signs_and_symptoms_at_hosp___23", ref = "checkbox" }
 
 [[observation]]
   name = "shortness_of_breath"
   date = { field = "ADMIT DATE" }
   phase = "admission"
-  is_present = { field = "signs_and_symptoms_at_hosp___14", values = { 1 = true } }
+  is_present = { field = "signs_and_symptoms_at_hosp___14", ref = "checkbox" }
 
 [[observation]]
   name = "skin_rash"
   date = { field = "ADMIT DATE" }
   phase = "admission"
-  is_present = { field = "signs_and_symptoms_at_hosp___26", values = { 1 = true } }
+  is_present = { field = "signs_and_symptoms_at_hosp___26", ref = "checkbox" }
 
 [[observation]]
   name = "sore_throat"
   date = { field = "ADMIT DATE" }
   phase = "admission"
-  is_present = { field = "signs_and_symptoms_at_hosp___25", values = { 1 = true } }
+  is_present = { field = "signs_and_symptoms_at_hosp___25", ref = "checkbox" }
 
 [[observation]]
   name = "vomiting_nausea"
   date = { field = "ADMIT DATE" }
   phase = "admission"
-  is_present = { field = "signs_and_symptoms_at_hosp___21", values = { 1 = true } }
+  is_present = { field = "signs_and_symptoms_at_hosp___21", ref = "checkbox" }
 
 [[observation]]
   name = "runny_nose"
   date = { field = "ADMIT DATE" }
   phase = "admission"
-  is_present = { field = "signs_and_symptoms_at_hosp___20", values = { 1 = true } }
+  is_present = { field = "signs_and_symptoms_at_hosp___20", ref = "checkbox" }
 
 [[observation]]
   name = "other_symptom"
@@ -554,7 +555,7 @@
   ] } }
   duration_type = "event"
   phase = "study"
-  is_present = { field = "complications___5", values = { 1 = true } }
+  is_present = { field = "complications___5", ref = "checkbox" }
   context = ['bacterial']
 
 [[observation]]
@@ -565,5 +566,5 @@
   ] } }
   duration_type = "event"
   phase = "study"
-  is_present = { field = "complications___14", values = { 1 = true } }
+  is_present = { field = "complications___14", ref = "checkbox" }
   context = ['COP']
diff --git a/isaric/parsers/ncov-france.toml b/isaric/parsers/ncov-france.toml
index 1acae08..73cff1a 100644
--- a/isaric/parsers/ncov-france.toml
+++ b/isaric/parsers/ncov-france.toml
@@ -207,8 +207,8 @@
     combinedType = "any"
     excludeWhen = "none"
     fields = [
-      { field = "ttt_ass_type___1", values = { 1 = true } },
-      { field = "ttt_ass_type___2", values = { 1 = true } },
+      { field = "ttt_ass_type___1", ref = "checkbox" },
+      { field = "ttt_ass_type___2", ref = "checkbox" },
     ]
 
   [visit.treatment_antimalarial_type]
@@ -343,20 +343,20 @@
   name = "abdominal_pain"
   phase = "admission"
   date = { ref = "admissionDate" }
-  is_present = { field = "signes_clin___2", values = { 1 = true } }
+  is_present = { field = "signes_clin___2", ref = "checkbox" }
   context = ["diarrhoea/abdominal pain"]
 
 [[observation]]
   name = "confusion"
   phase = "admission"
   date = { ref = "admissionDate" }
-  is_present = { field = "signes_clin___7", values = { 1 = true } }
+  is_present = { field = "signes_clin___7", ref = "checkbox" }
 
 [[observation]]
   name = "cough"
   phase = "admission"
   date = { ref = "admissionDate" }
-  is_present = { field = "signes_clin___1", values = { 1 = true } }
+  is_present = { field = "signes_clin___1", ref = "checkbox" }
 
 [[observation]]
   name = "diastolic_blood_pressure_mmHg"
@@ -368,20 +368,20 @@
   name = "diarrhoea"
   phase = "admission"
   date = { ref = "admissionDate" }
-  is_present = { field = "signes_clin___2", values = { 1 = true } }
+  is_present = { field = "signes_clin___2", ref = "checkbox" }
   context = ["diarrhoea/abdominal pain"]
 
 [[observation]]
   name = "headache"
   phase = "admission"
   date = { ref = "admissionDate" }
-  is_present = { field = "signes_clin___4", values = { 1 = true } }
+  is_present = { field = "signes_clin___4", ref = "checkbox" }
 
 [[observation]]
   name = "history_of_fever"
   phase = "admission"
   date = { ref = "admissionDate" }
-  is_present = { field = "signes_clin___5", values = { 1 = true } }
+  is_present = { field = "signes_clin___5", ref = "checkbox" }
 
 [[observation]]
   name = "glasgow_coma_score"
@@ -437,7 +437,7 @@
   [observation.is_present]
     combinedType = "any"
     fields = [
-      { field = "signes_clin___8", values = { 1 = true } },
+      { field = "signes_clin___8", ref = "checkbox" },
       # { field = "signes_clin___9", values = { 1 = true } },
     ]
 
@@ -445,7 +445,7 @@
   name = "loss_of_smell"
   phase = "admission"
   date = { ref = "admissionDate" }
-  is_present = { field = "signes_clin___8", values = { 1 = true } }
+  is_present = { field = "signes_clin___8", ref = "checkbox" }
 
 [[observation]]
   name = "mean_arterial_blood_pressure_mmHg"
@@ -457,13 +457,13 @@
   name = "muscle_aches"
   phase = "admission"
   date = { ref = "admissionDate" }
-  is_present = { field = "signes_clin___6", values = { 1 = true } }
+  is_present = { field = "signes_clin___6", ref = "checkbox" }
 
 [[observation]]
   name = "musculoskeletal_pain"
   phase = "admission"
   date = { ref = "admissionDate" }
-  is_present = { field = "signes_clin___6", values = { 1 = true } }
+  is_present = { field = "signes_clin___6", ref = "checkbox" }
 
 [[observation]]
   name = "oxygen_flow_rate"
@@ -554,14 +554,14 @@
   start_date = { ref = "admissionDate" }
   date = { field = "shosp_d", source_date = "%Y-%m-%d" }
   duration_type = "event"
-  is_present = { field = "compl_type___1", values = { 1 = true }, description = "VAP" }
+  is_present = { field = "compl_type___1", ref = "checkbox", description = "VAP" }
   context = ["Ventilator associated pneumonia"]
 
 [[observation]]
   name = "shortness_of_breath"
   phase = "admission"
   date = { ref = "admissionDate" }
-  is_present = { field = "signes_clin___9", values = { 1 = true } }
+  is_present = { field = "signes_clin___9", ref = "checkbox" }
 
 [[observation]]
   name = "systolic_blood_pressure_mmHg"
diff --git a/isaric/parsers/ncov-malaysia.toml b/isaric/parsers/ncov-malaysia.toml
index 182b5a7..970b084 100644
--- a/isaric/parsers/ncov-malaysia.toml
+++ b/isaric/parsers/ncov-malaysia.toml
@@ -489,10 +489,10 @@
     fields = [
       { field = "mx_antimalarial", ref = "Y/N" },
       { field = "antimalarial_dc", ref = "Y/N" },
-      { field = "mx_antimalarial_type___1", values = { 1 = true } },
-      { field = "mx_antimalarial_type___2", values = { 1 = true } },
-      { field = "type_antimalarial_dc___1", values = { 1 = true } },
-      { field = "type_antimalarial_dc___2", values = { 1 = true } },
+      { field = "mx_antimalarial_type___1", ref = "checkbox" },
+      { field = "mx_antimalarial_type___2", ref = "checkbox" },
+      { field = "type_antimalarial_dc___1", ref = "checkbox" },
+      { field = "type_antimalarial_dc___2", ref = "checkbox" },
     ]
 
   [visit.treatment_antimalarial_type]
diff --git a/isaric/parsers/western-australia.toml b/isaric/parsers/western-australia.toml
index 96574a3..5519cff 100644
--- a/isaric/parsers/western-australia.toml
+++ b/isaric/parsers/western-australia.toml
@@ -31,14 +31,12 @@
     aggregation = "lastNotNull"
     schema = "../../schemas/dev/observation.schema.json"
 
-  [adtl.defs."Y/N/NK".values]
+  [adtl.defs."Y/N".values] # use in observations where NK shouldn't be mapped
     1 = true
     2 = false
-    3 = false
 
-  [adtl.defs."Y/N".values] # use in observations where NK shouldn't be mapped
+  [adtl.defs.checkbox.values]
     1 = true
-    2 = false
 
 [adtl.defs.admissionDateHierarchy]
   combinedType = "firstNonNull"
@@ -100,12 +98,12 @@
   [subject.works_healthcare]
     field = "healthwork_erterm"
     description = "Healthcare Worker?"
-    ref = "Y/N/NK"
+    ref = "Y/N"
 
   [subject.works_lab]
     field = "labwork_erterm"
     description = "Laboratory worker?"
-    ref = "Y/N/NK"
+    ref = "Y/N"
 
   [subject.pregnancy]
     field = "pregyn_rptestcd"
@@ -119,12 +117,12 @@
   [subject.has_asplenia]
     field = "asplenia_mhyn"
     description = "Asplenia"
-    ref = "Y/N/NK"
+    ref = "Y/N"
 
   [subject.has_tuberculosis]
     field = "tb_mhyn"
     description = "Tuberculosis"
-    ref = "Y/N/NK"
+    ref = "Y/N"
 
   [subject.has_hiv]
     combinedType = "any"
@@ -137,12 +135,12 @@
   [subject.has_hypertension]
     field = "hypertension_mhyn"
     description = "Hypertension"
-    ref = "Y/N/NK"
+    ref = "Y/N"
 
   [subject.has_malignant_neoplasm]
     field = "malignantneo_mhyn"
     description = "Malignant neoplasm"
-    ref = "Y/N/NK"
+    ref = "Y/N"
 
   [subject.has_smoking]
     field = "smoking_mhyn"
@@ -152,27 +150,27 @@
   [subject.has_asthma]
     field = "asthma_mhyn"
     description = "Asthma"
-    ref = "Y/N/NK"
+    ref = "Y/N"
 
   [subject.has_chronic_cardiac_disease]
     field = "chroniccard_mhyn"
     description = "Chronic cardiac disease"
-    ref = "Y/N/NK"
+    ref = "Y/N"
 
   [subject.has_chronic_kidney_disease]
     field = "renal_mhyn"
     description = "Chronic kidney disease"
-    ref = "Y/N/NK"
+    ref = "Y/N"
 
   [subject.has_diabetes]
     field = "diabetes_mhyn"
     description = "Diabetes"
-    ref = "Y/N/NK"
+    ref = "Y/N"
 
   [subject.has_liver_disease]
     field = "liver_mhyn"
     description = "Chronic liver disease"
-    ref = "Y/N/NK"
+    ref = "Y/N"
 
   [subject.has_malnutrition]
     field = "malnutrition_vsorres"
@@ -198,10 +196,10 @@
     description = "ICU or High Dependency admission"
     combinedType = "any"
     fields = [
-      { field = "overall_icu_hoterm", ref = "Y/N/NK", description = "ICU or High Dependency admission?" },
+      { field = "overall_icu_hoterm", ref = "Y/N", description = "ICU or High Dependency admission?" },
       { field = "overall_icu_hoyn", values = { 1 = true, 2 = false }, description = "Still in ICU at outcome?" },
-      { field = "daily_icu_hoterm", ref = "Y/N/NK", description = "ICU or High Dependency admission?" },
-      { field = "icu_hoterm", ref = "Y/N/NK", description = "ICU or High Dependency admission on the first day of admission?" },
+      { field = "daily_icu_hoterm", ref = "Y/N", description = "ICU or High Dependency admission?" },
+      { field = "icu_hoterm", ref = "Y/N", description = "ICU or High Dependency admission on the first day of admission?" },
     ]
 
 [visit]
@@ -235,10 +233,10 @@
     description = "ICU or High Dependency admission"
     combinedType = "any"
     fields = [
-      { field = "overall_icu_hoterm", ref = "Y/N/NK", description = "ICU or High Dependency admission?" },
+      { field = "overall_icu_hoterm", ref = "Y/N", description = "ICU or High Dependency admission?" },
       { field = "overall_icu_hoyn", values = { 1 = true, 2 = false }, description = "Still in ICU at outcome?" },
-      { field = "daily_icu_hoterm", ref = "Y/N/NK", description = "ICU or High Dependency admission?" },
-      { field = "icu_hoterm", ref = "Y/N/NK", description = "ICU or High Dependency admission on the first day of admission?" },
+      { field = "daily_icu_hoterm", ref = "Y/N", description = "ICU or High Dependency admission?" },
+      { field = "icu_hoterm", ref = "Y/N", description = "ICU or High Dependency admission on the first day of admission?" },
     ]
 
   [visit.icu_admission_dates]
@@ -252,17 +250,17 @@
     description = "Dialysis"
     combinedType = "any"
     fields = [
-      { field = "overall_rrt_prtrt", ref = "Y/N/NK", description = "Renal replacement therapy (RRT) or dialysis?" },
-      { field = "daily_rrt_prtrt", ref = "Y/N/NK", description = "Renal replacement therapy (RRT) or dialysis?" },
+      { field = "overall_rrt_prtrt", ref = "Y/N", description = "Renal replacement therapy (RRT) or dialysis?" },
+      { field = "daily_rrt_prtrt", ref = "Y/N", description = "Renal replacement therapy (RRT) or dialysis?" },
     ]
 
   [visit.treatment_inotropes_vasopressors]
     description = "Inotropes/vasopressors"
     combinedType = "any"
     fields = [
-      { field = "overall_inotrop_cmtrt", ref = "Y/N/NK", description = "Inotropes/vasopressors?" },
-      { field = "daily_inotrop_cmtrt", ref = "Y/N/NK", description = "Inotropes/vasopressors?" },
-      { field = "inotrop_cmtrt", ref = "Y/N/NK", description = "Inotropes/vasopressors on the first day of admission?" },
+      { field = "overall_inotrop_cmtrt", ref = "Y/N", description = "Inotropes/vasopressors?" },
+      { field = "daily_inotrop_cmtrt", ref = "Y/N", description = "Inotropes/vasopressors?" },
+      { field = "inotrop_cmtrt", ref = "Y/N", description = "Inotropes/vasopressors on the first day of admission?" },
     ]
 
   [visit.treatment_ecmo]
@@ -271,33 +269,33 @@
 
     [[visit.treatment_ecmo.fields]]
       field = "overall_extracorp_prtrt"
-      ref = "Y/N/NK"
+      ref = "Y/N"
       description = "Extracorporeal (ECMO) support?"
 
     [[visit.treatment_ecmo.fields]]
       field = "daily_extracorp_prtrt"
-      ref = "Y/N/NK"
+      ref = "Y/N"
       description = "Extracorporeal (ECMO) support?"
 
     [[visit.treatment_ecmo.fields]]
       field = "extracorp_prtrt"
-      ref = "Y/N/NK"
+      ref = "Y/N"
       description = "Extracorporeal (ECMO) support on the first day of admission?"
 
 [visit.treatment_cardiovascular_support]
   combinedType = "any"
   fields = [
-    { fieldPattern = ".*extracorp_prtrt", ref = "Y/N/NK" },
-    { fieldPattern = "inotrop_cmtrt", ref = "Y/N/NK" },
+    { fieldPattern = ".*extracorp_prtrt", ref = "Y/N" },
+    { fieldPattern = "inotrop_cmtrt", ref = "Y/N" },
   ]
 
 [visit.treatment_corticosteroid]
   description = "Corticosteroid"
   combinedType = "any"
   fields = [
-    { field = "overall_corticost_cmyn", ref = "Y/N/NK", description = "Corticosteroid?" },
-    { field = "daily_corticost_cmyn", ref = "Y/N/NK", description = "Corticosteroid?" },
-    { field = "corticost_cmyn", ref = "Y/N/NK", description = "Corticosteroid on the first day of admission?" },
+    { field = "overall_corticost_cmyn", ref = "Y/N", description = "Corticosteroid?" },
+    { field = "daily_corticost_cmyn", ref = "Y/N", description = "Corticosteroid?" },
+    { field = "corticost_cmyn", ref = "Y/N", description = "Corticosteroid on the first day of admission?" },
   ]
 
 [visit.treatment_corticosteroid_type]
@@ -316,49 +314,49 @@
   description = "Oxygen therepy"
   combinedType = "any"
   fields = [
-    { fieldPattern = ".*oxygen_cmoccur", ref = "Y/N/NK", description = "Oxygen therapy?" },
-    { fieldPattern = "overall_oxygen_cmtype.*", values = { 1 = true } },
+    { fieldPattern = ".*oxygen_cmoccur", ref = "Y/N", description = "Oxygen therapy?" },
+    { fieldPattern = "overall_oxygen_cmtype.*", ref = "checkbox" },
     { fieldPattern = ".*oxygen_cmtype", values = { 1 = true, 2 = true, 3 = true, 4 = true, 5 = true } },
-    { fieldPattern = ".*invasive_proccur", ref = "Y/N/NK", description = "Invasive ventilation?" },
-    { fieldPattern = ".*noninvasive_proccur", ref = "Y/N/NK", description = "Non-invasive ventilation?" },
-    { fieldPattern = ".*extracorp_prtrt", ref = "Y/N/NK" },
+    { fieldPattern = ".*invasive_proccur", ref = "Y/N", description = "Invasive ventilation?" },
+    { fieldPattern = ".*noninvasive_proccur", ref = "Y/N", description = "Non-invasive ventilation?" },
+    { fieldPattern = ".*extracorp_prtrt", ref = "Y/N" },
   ]
 
 [visit.treatment_prone_position]
   description = "Prone Positioning"
   combinedType = "any"
   fields = [
-    { field = "overall_prone_prtrt", ref = "Y/N/NK", description = "Prone positioning?" },
-    { field = "daily_prone_prtrt", ref = "Y/N/NK", description = "Prone positioning?" },
-    { field = "prone_prtrt", ref = "Y/N/NK", description = "Prone position on first day of admission?" },
+    { field = "overall_prone_prtrt", ref = "Y/N", description = "Prone positioning?" },
+    { field = "daily_prone_prtrt", ref = "Y/N", description = "Prone positioning?" },
+    { field = "prone_prtrt", ref = "Y/N", description = "Prone position on first day of admission?" },
   ]
 
 [visit.treatment_invasive_ventilation]
   description = "Invasive ventilation"
   combinedType = "any"
   fields = [
-    { field = "overall_invasive_proccur", ref = "Y/N/NK", description = "Invasive ventilation?" },
-    { field = "daily_invasive_proccur", ref = "Y/N/NK", description = "Invasive ventilation?" },
-    { field = "invasive_proccur", ref = "Y/N/NK", description = "Invasive ventilation on first day of admission?" },
+    { field = "overall_invasive_proccur", ref = "Y/N", description = "Invasive ventilation?" },
+    { field = "daily_invasive_proccur", ref = "Y/N", description = "Invasive ventilation?" },
+    { field = "invasive_proccur", ref = "Y/N", description = "Invasive ventilation on first day of admission?" },
   ]
 
 [visit.treatment_antifungal_agent]
   description = "Antifungal"
   combinedType = "any"
   fields = [
-    { field = "overall_antifung_cmyn", ref = "Y/N/NK", description = "Antifungal agent?" },
-    { field = "daily_antifung_cmyn", ref = "Y/N/NK", description = "Antifungal agent?" },
-    { field = "antifung_cmyn", ref = "Y/N/NK", description = "Antifungal agent on the first day of admission?" },
+    { field = "overall_antifung_cmyn", ref = "Y/N", description = "Antifungal agent?" },
+    { field = "daily_antifung_cmyn", ref = "Y/N", description = "Antifungal agent?" },
+    { field = "antifung_cmyn", ref = "Y/N", description = "Antifungal agent on the first day of admission?" },
   ]
 
 [visit.treatment_antivirals]
   description = "Antiviral"
   combinedType = "any"
   fields = [
-    { field = "overall_antiviral_cmyn", ref = "Y/N/NK", description = "Antiviral agent?" },
-    { field = "daily_antiviral_cmyn", ref = "Y/N/NK", description = "Antiviral agent?" },
-    { field = "antiviral_cmyn", ref = "Y/N/NK", description = "Antiviral agent on the first day of admission?" },
-    { fieldPattern = ".*exper_cmtype___3", values = { 1 = true } },
+    { field = "overall_antiviral_cmyn", ref = "Y/N", description = "Antiviral agent?" },
+    { field = "daily_antiviral_cmyn", ref = "Y/N", description = "Antiviral agent?" },
+    { field = "antiviral_cmyn", ref = "Y/N", description = "Antiviral agent on the first day of admission?" },
+    { fieldPattern = ".*exper_cmtype___3", ref = "checkbox" },
   ]
 
 
@@ -380,9 +378,9 @@
   description = "Antibiotics"
   combinedType = "any"
   fields = [
-    { field = "overall_antibiotic_cmyn", ref = "Y/N/NK", description = "Antibiotic?" },
-    { field = "daily_antibiotic_cmyn", ref = "Y/N/NK", description = "Antibiotic?" },
-    { field = "antibiotic_cmyn", ref = "Y/N/NK", description = "Antibiotic on the first day of admission?" },
+    { field = "overall_antibiotic_cmyn", ref = "Y/N", description = "Antibiotic?" },
+    { field = "daily_antibiotic_cmyn", ref = "Y/N", description = "Antibiotic?" },
+    { field = "antibiotic_cmyn", ref = "Y/N", description = "Antibiotic on the first day of admission?" },
   ]
 
 [visit.treatment_other]
@@ -408,9 +406,9 @@
   description = "Noninvasive ventilation"
   combinedType = "any"
   fields = [
-    { field = "overall_noninvasive_proccur", ref = "Y/N/NK", description = "Invasive ventilation?" },
-    { field = "daily_noninvasive_proccur", ref = "Y/N/NK", description = "Invasive ventilation?" },
-    { field = "noninvasive_proccur", ref = "Y/N/NK", description = "Invasive ventilation on first day of admission?" },
+    { field = "overall_noninvasive_proccur", ref = "Y/N", description = "Invasive ventilation?" },
+    { field = "daily_noninvasive_proccur", ref = "Y/N", description = "Invasive ventilation?" },
+    { field = "noninvasive_proccur", ref = "Y/N", description = "Invasive ventilation on first day of admission?" },
   ]
 
 [visit.treatment_ace_inhibitors]
@@ -419,12 +417,12 @@
 
   [[visit.treatment_ace_inhibitors.fields]]
     field = "daily_ace_cmoccur"
-    ref = "Y/N/NK"
+    ref = "Y/N"
     description = "Angiotension converting enzyme inhibitors (ACE inhibitors)?"
 
   [[visit.treatment_ace_inhibitors.fields]]
     field = "ace_cmoccur"
-    ref = "Y/N/NK"
+    ref = "Y/N"
     description = "Angiotensin converting enzyme inhibitors (ACE) on the first day of admission?"
 
 [visit.treatment_arb]
@@ -433,12 +431,12 @@
 
   [[visit.treatment_arb.fields]]
     field = "daily_arb_cmoccur"
-    ref = "Y/N/NK"
+    ref = "Y/N"
     description = "Angiotensin II receptor blockers (ARBs)?"
 
   [[visit.treatment_arb.fields]]
     field = "arb_cmoccur"
-    ref = "Y/N/NK"
+    ref = "Y/N"
     description = "Angiotensin II receptor blockers (ARBs) on the first day of admission?"
 
 
@@ -446,17 +444,17 @@
   description = "Antimalarial"
   combinedType = "any"
   fields = [
-    { field = "overall_antimal_cmyn", ref = "Y/N/NK", description = "Antimalarial agent?" },
-    { field = "daily_antimal_cmyn", ref = "Y/N/NK", description = "Antimalarial agent?" },
-    { field = "antimal_cmyn", ref = "Y/N/NK", description = "Antimalarial agent on the first day of admission?" },
-    { fieldPattern = ".*exper_cmtype___1", values = { 1 = true } },
-    { fieldPattern = ".*exper_cmtype___2", values = { 1 = true } },
-    { fieldPattern = ".*antimal_cmtype___1", values = { 1 = true } },
-    { fieldPattern = ".*antimal_cmtype___2", values = { 1 = true } },
-    { fieldPattern = ".*antimal_cmtype___3", values = { 1 = true } },
-    { fieldPattern = ".*antimal_cmtype___4", values = { 1 = true } },
-    { fieldPattern = ".*antimal_cmtype___5", values = { 1 = true } },
-    { fieldPattern = ".*antimal_cmtype___6", values = { 1 = true } },
+    { field = "overall_antimal_cmyn", ref = "Y/N", description = "Antimalarial agent?" },
+    { field = "daily_antimal_cmyn", ref = "Y/N", description = "Antimalarial agent?" },
+    { field = "antimal_cmyn", ref = "Y/N", description = "Antimalarial agent on the first day of admission?" },
+    { fieldPattern = ".*exper_cmtype___1", ref = "checkbox" },
+    { fieldPattern = ".*exper_cmtype___2", ref = "checkbox" },
+    { fieldPattern = ".*antimal_cmtype___1", ref = "checkbox" },
+    { fieldPattern = ".*antimal_cmtype___2", ref = "checkbox" },
+    { fieldPattern = ".*antimal_cmtype___3", ref = "checkbox" },
+    { fieldPattern = ".*antimal_cmtype___4", ref = "checkbox" },
+    { fieldPattern = ".*antimal_cmtype___5", ref = "checkbox" },
+    { fieldPattern = ".*antimal_cmtype___6", ref = "checkbox" },
   ]
 
 [visit.treatment_antimalarial_type]
@@ -478,9 +476,9 @@
   combinedType = "any"
   fields = [
     { fieldPattern = ".*oxygen_cmtype", values = { 1 = true, 2 = false, 3 = true, 4 = true, 5 = false } },
-    { field = "overall_oxygen_cmtype___1", values = { 1 = true } },
-    { field = "overall_oxygen_cmtype___3", values = { 1 = true } },
-    { field = "overall_oxygen_cmtype___4", values = { 1 = true } },
+    { field = "overall_oxygen_cmtype___1", ref = "checkbox" },
+    { field = "overall_oxygen_cmtype___3", ref = "checkbox" },
+    { field = "overall_oxygen_cmtype___4", ref = "checkbox" },
   ]
 
 [visit.treatment_high_flow_nasal_cannula]
@@ -489,7 +487,7 @@
 
   [[visit.treatment_high_flow_nasal_cannula.fields]]
     field = "overall_oxygen_cmtype___2"
-    values = { 1 = true }
+    ref = "checkbox"
 
   [[visit.treatment_high_flow_nasal_cannula.fields]]
     field = "daily_oxygen_cmtype"
@@ -505,26 +503,26 @@
 
   [[visit.treatment_nsaid.fields]]
     field = "overall_nsaid_cmyn"
-    ref = "Y/N/NK"
+    ref = "Y/N"
     description = "Non-steroidal anti-inflammatory (NSAID)?"
 
   [[visit.treatment_nsaid.fields]]
     field = "daily_nsaid_cmoccur"
-    ref = "Y/N/NK"
+    ref = "Y/N"
     description = "Non-steroidal anti-inflammatory (NSAID)?"
 
   [[visit.treatment_nsaid.fields]]
     field = "nsaid_cmoccur"
-    ref = "Y/N/NK"
+    ref = "Y/N"
     description = "Non-steroidal anti-inflammatory (NSAID) on first day of admission?"
 
 [visit.treatment_intravenous_fluids]
   description = "IV fluids"
   combinedType = "any"
   fields = [
-    { field = "overall_iv_fluids_cmyn", ref = "Y/N/NK", description = "Intraveonous fluids?" },
-    { field = "daily_iv_fluids_cmyn", ref = "Y/N/NK", description = "Intraveonous fluids?" },
-    { field = "iv_fluids_cmyn", ref = "Y/N/NK", description = "Intraveonous fluids on the first day of admission?" },
+    { field = "overall_iv_fluids_cmyn", ref = "Y/N", description = "Intraveonous fluids?" },
+    { field = "daily_iv_fluids_cmyn", ref = "Y/N", description = "Intraveonous fluids?" },
+    { field = "iv_fluids_cmyn", ref = "Y/N", description = "Intraveonous fluids on the first day of admission?" },
   ]
 
 [visit.outcome]
@@ -559,7 +557,7 @@
   name = "bleeding_haemorrhage"
   date = { ref = "admissionDateHierarchy" }
   phase = "admission"
-  is_present = { field = "bleed_ceoccur_v2", ref = "Y/N/NK" }
+  is_present = { field = "bleed_ceoccur_v2", ref = "Y/N" }
 
 [[observation]]
   name = "cough"
@@ -568,7 +566,7 @@
   [observation.is_present]
     combinedType = "any"
     fields = [
-      { field = "cough_ceoccur_v2", ref = "Y/N/NK" },
+      { field = "cough_ceoccur_v2", ref = "Y/N" },
       { field = "coughsput_ceoccur_v2", ref = "Y/N" },
       { field = "coughhb_ceoccur_v2", ref = "Y/N" },
     ]
@@ -577,7 +575,7 @@
   name = "cough_dry"
   date = { ref = "admissionDateHierarchy" }
   phase = "admission"
-  is_present = { field = "cough_ceoccur_v2", ref = "Y/N/NK" }
+  is_present = { field = "cough_ceoccur_v2", ref = "Y/N" }
 
 [[observation]]
   name = "cough_with_sputum_production"