The preprocessing and analysis of the data was conducted in the R project for statistical computing. The RMarkdown script used to generate this document and all the resulting data can be downloaded under this link. Through executing main.Rmd, the herein described process can be reproduced and this document can be generated. In the course of this, data from the folder input will be processed and results will be written to output. There are multiple RData files in the folder rdata. They are emitted in the chunks of main.Rmd and saved for a faster process after the first execution. The download stored to input/ignore/pubmed could not be saved in this git repository, because of it's size (1.4 GB). Find out how to get your own version of the xml file below.
The code for the herein described process can also be freely downloaded from https://github.com/srfdata/2019-02-clinical-trials.
2019-02-clinical-trials by SRF Data is licensed under a Creative Commons Namensnennung - Attribution ShareAlike 4.0 International License.
| Attribute | Type | Description |
|---|---|---|
| unique_id | String | Unique identifier assigned by SRF |
| primary | String | Trial identification number |
| size | Numeric | Number of people participating in study (total, world wide) |
| study_type | Factor | Type of study, either Interventional or Observational |
| status | Factor | Status of the trial, either Completed, Ongoing, Terminated or Unknown |
| primary_sponsor | String | The primary sponsor of the trial (responsible for updating register information) |
| leading_institution | String | The (scientifically) leading institution of the trial |
| registration_date | Date | Date the trial was registered in the registry |
| start_date | Date | Date on which the enrollment process started |
| end_date | Date | Date on which the enrollment process ended |
| results_submitted | Boolean | Equals true if a result was submitted to the trial registry |
| publication_found | Boolean | Equals true if the trial ID was found in cochrane / pubmed |
| source | Factor | Shows in which registry this trial was found, either NCT, EUCTR or DRKS |
| has_g_scholar_results | Boolean | Equals true if google scholar returned any results when queried with the trial id |
| primary_sponsor_simple | String | Simplified Name of primary sponsor (mainly done for swiss institutions) |
| leading_institution_simple | String | Simplified Name of leading institution (mainly done for swiss institutions) |
On the flow chart below, we describe how we tried to find all trials related to Switzerland and how we evaluated whether a publication for that trial exitsts.
We searched the following registers by selecting Switzerland OR Schweiz as a country of recruitement:
→ http://apps.who.int/trialsearch/AdvSearch.aspx
Downloaded 01/14/2019 at 12:35 CET by setting recruitment status to ALL and chosing Export all trials to XML.
→ https://clinicaltrials.gov/ct2/results?cond=&term=Switzerland&cntry=&state=&city=&dist=
Downloaded 01/14/2019 at 12:31 CET via Download > For Advanced Users: Full Study Record XML Download.
→ https://www.drks.de/drks_web/navigate.do?navigationId=search&reset=true
Downloaded 01/24/2019 at 13:20 CET as csv.
You can query PubMed for all publications with a linked NCT ClinicalTrials.gov ID:
→ https://www.ncbi.nlm.nih.gov/pubmed/?cmd=Search&term=clinicaltrials.gov%5bsi%5d
We also search the following terms and saved the result as xml by choosing Send to > File > XML:
EUDRACT*EUCTR*NCT0*DRKS*
https://www.ncbi.nlm.nih.gov/pubmed?term=(((EUDRACT*)%20OR%20EUCTR*)%20OR%20NCT0*)%20OR%20DRKS*
Downloaded 01/14/2019 at 10:56 CET.
You can read more about finding results of studies on ClinicalTrials.gov.
Downloaded 01/14/2019 at 10:25 CET by searching ID wildcards e.g. *NCT0* in ti, ab, kw (Title, Abstract, Keywords).
Limit the years to get the total number of trials below the export limit of 20k.
Search terms:
NCT0*EUCTR*EUDRACT*Switzerland
Read more about the Cochrane CENTRAL database here.
The swiss registry for trials is only a secondary register. All the trials in it must also be registered in one of the primary registers (European, German, American registers). It does not contain any information about whether a trial was started or completed.