Excluded, not dismissed: enhancing benefit in clinical research

Why do GPs exclude patients from participating in research? An exploration of adherence to and divergence from trial criteria

BACKGROUND

The role of GPs in recruiting or excluding participants critically underpins the feasibility, external validity and generalizability of primary care research. A better understanding of this role is needed.

AIM

To investigate why GPs excluded potentially eligible participants from a large scale randomized controlled trial (RCT), to determine the proportion of patients excluded on account of trial eligibility compared with other reasons, and to explore the impact of such exclusions on the management and generalizability of RCTs.

DESIGN AND SETTING

Secondary analysis of data from the CoBalT study, a multi-centre general-practice-based RCT investigating cognitive behavioural therapy as an adjunct to pharmacotherapy for treatment-resistant depression.

METHOD

GPs were asked to screen patient lists generated from computerized record searches for trial eligibility and to provide narrative reasons for excluding patients. These reasons were coded independently by two researchers, with a third researcher resolving discrepancies.

RESULTS

Thirty-one percent (4750/15,379) of patients were excluded at the GP screening stage, including 663 on patient lists that remained unscreened. Of the 4087 actively excluded patients, 67% were excluded on account of trial exclusion criteria, 20% for other criteria (half of which were comorbid conditions) and 13% without reason.

CONCLUSION

Clear, comprehensive criteria, particularly with regards to comorbidities, are required for GPs to confidently screen patients for potential participation in research. Future studies should promote inclusivity and encourage GPs to adopt a liberal approach when screening patient lists. This would enhance the validity and generalizability of primary care research and encourage greater patient autonomy.