Phase 3 trials evaluating drugs & biologicals – studies located in Germany, UK, and France => ~ 50% unpublished

ClinicalTrials.gov search query (Nov 16, 2014): Closed Studies | Interventional Studies | Germany | United Kingdom | France | Phase 3 | received from 01/01/2002 to 01/01/2014

Results: 4496 studies – 67.2% of studies registered in Europe using the above search criteria

Search of  Closed Studies   Interventional Studies   Phase 3   received from 01 01 2002 to 01 01 2014 - Results on Map - ClinicalTrials.gov

View the updated map for this search query on ClinicalTrials.gov

HOW TO ESTIMATE THE PERCENTAGE OF UNPUBLISHED TRIALS?

1. Download the Search Results

Search of  Closed Studies   Interventional Studies   Germany   United Kingdom   France   Phase 3   received from 01 01 2002 to 01 01 2014 - List Results - ClinicalTrials.gov

2. Extract the zip file (search_result.zip).

3. Open the archive (study_fields.csv) using Google Spreadsheet or Microsoft Excel.

4496 studies found for  Closed Studies   Interventional Studies   Germany   United Kingdom   France   Phase 3   received from 01 01 2002 to 01 01 2014 - Google Sheets

4. Copy and paste NCT numbers in a different column – replace the letter “N” for “OR N”

study_fields 67 - Google Sheets (1) study_fields 67 - Google Sheets (3)

5. Copy & Paste expert search terms and perform a PubMed Search Query

nct00330317 or nct00708656 or nct00241527 or nct00128167 or nct0066170 - PubMed - NCBI

6. Analyze the results:
– Records not found (PubMed): 1189 out of 1995 ClinicalTrials.gov records (60%)
– 
806 ClinicalTrials.gov records found —> matching 1349 PubMed articles

Document sans titre - Google Docs (6)

nct00330317 or nct00708656 or nct00241527 or nct00128167 or nct0066170 - PubMed - NCBI (2)

https://docs.google.com/spreadsheets/d/1IEGtD0cj7_ZVuynZeEwygLj244lHGLNxbu6oMy8OAz8/edit#gid=840653898

PubMed search query  1349 results   NCT Numbers  n = 1995  ---  Closed Studies   Interventional Studies   Germany   United Kingdom   France   Phase 3   received from 01 01 2002 to 01 01 2014  Search Date Nov 16, 2014  - Google Sheets

7. Perform a second search query on Embase for records not found in PubMed (n = 1189)
Filter: publication type = article
Results = 332 articles

Embase (1)

https://docs.google.com/spreadsheets/d/1_b0rchrdH23w9xQMdYfpsBISCarnjZA3T21FXfS8mmk/edit#gid=1909169334

Embase  Drug   Biological   Completed Before Jan 2011   Closed Studies   Interventional Studies   Germany   United Kingdom   France   Phase 3   received from 01 01 2002 to 01 01 2014 ---- Search Query of 1189 records not found in PubMed - G

 

FINAL NOTES & COMMENTS:

Manual revision of identified articles in PubMed and Embase is necessary to estimate precisely the percentage of published and unpublished clinical trials. Some articles reporting the results of trials not found on PubMed and Embase can be identified using other academic databases (e.g., EBSCO Discovery and Google Scholar) and performing search queries with different registry fields (e.g., other IDs). Nonetheless, I know from previous analysis that PubMed & Embase can identify the majority of published clinical trial registries.

For example:

Unpublished US phase 3 ClinicalTrials.gov registries (intervention: drugs and biologicals) completed before January 2011 and registered between Jan 1st, 2002 to Jan 1st, 2014.(1, 2)

US phase 3 unpublished trials.010

Total number of registries: 2957

1. Published 48.2% (n = 1450)

– PubMed 80% (n = 1160)
– Embase 18.5% (n = 269)
– EBSCO Discovery 1.5% (n = 21)

2. Unpublished 50.8% (n = 1507)

It is important to understand that the estimation of unpublished studies in a sample of clinical trial registries is only a minor part of the total analysis. Other variables such as the time of registration and the beginning of patient recruitment are also very important (see Table Below).

Chi_square_statistics_of_US_phase_3_trials__published__Y_N____results__Y_N____retrospectiv... (1)

Other variables such as the location of patient recruitment can be also analyzed. For example, agomelatine registered studies (Figure below). However, the analysis of locations is easier to carry out downloading registries from WHO ICTRP (ClinicalTrials.gov locations registry fields are not available for download).(3)

Published and unpublished agomelatine study registries - locations and estimated patient recruitment

 

With this information it can be estimated that the percentage of unpublished phase 3 clinical trials, evaluating drugs and biologicals, recruiting patients in locations from three different European countries (i.e., Germany, United Kingdom, and France), registered between January 1st 2002 and January 1st 2014, and completed before January 1st, 2011 is…

Around 50% ——-> UNPUBLISHED

A more precise estimate will be disclosed after manual verification of published and unpublished clinical trial registries.

References

1. http://www.bmj.com/content/347/bmj.f1881/rr/762606

2. http://www.bmj.com/content/347/bmj.f6449/rr/690626

3. http://www.bmj.com/content/348/bmj.g1888/rr/762419

  1 comment for “Phase 3 trials evaluating drugs & biologicals – studies located in Germany, UK, and France => ~ 50% unpublished

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