Het deelnemen aan klinisch onderzoek verbetert therapietrouw*

Objective

To investigate the effect of participation in a clinical trial on adherence and persistence to treatment in patients with hypertension.

Design

Retrospective, observational cohort study.

Method

Between 2001 and 2004, the trial entitled, "Home versus Office blood pressure Measurements: Reduction of Unnecessary treatment Study" (HOMERUS) was conducted. Pharmacy refill data on 182 participants from the period 1999-2009 were obtained. Based on this data, adherence to treatment was compared for the periods before, during, and after the trial. Persistence to medication was investigated for the period after termination of the trial.

Results

Refill data were available on 22,600 prescriptions. Participation in the HOMERUS trial significantly increased refill adherence: from 90.6 to 95.6% (p < 0.001). After the trial period, refill adherence fell to 91.8% (p < 0.001), no different to adherence data from before the start of the trial (p = 0.45). Besides adherence to trial medication, adherence to non-trial related drugs also increased from 77.6 to 89.6% (p < 0.001) as a consequence of trial participation. Median persistence was 1424 days after termination of the trial. The participants classified as adherent (> 90%) continued taking the study medication longer than participants classified as non-adherent: 1440 versus 1000 days (odds ratio: 0.66; 95% confidence interval: 0.45-0.98).

Conclusion

Participation in a clinical trial significantly increases adherence to both trial- and non-trial-related treatment; this can possibly be explained by trial participants' heightened involvement in their conditions and treatments.

Conflict of interest: P.W. de Leeuw is chief editor of the Nederlands Tijdschrift voor Geneeskunde (Dutch Journal of Medicine), C. Neef is a member of the Dutch Medicines Evaluation Board and W.J.Verberk is employed by Microlife Corporation, Taipei, Taiwan. Financial support: This study was partially subsidised by ZonMW (project no. 945-01-043).