Strengths and limitations of the study
RECRUITMENT
This study had numerous strengths: To counter selection bias at recruitment, patients were asked systematically and consecutively in the general practice when picking up their refill prescription for PPI. Medical assistants proposed to participate in a study to discuss medication status of their stomach medication with their physician; a possible discontinuation was not yet addressed at this point.By selecting three study sites across federal state lines, the results were not localized and possible differences in PPI prescription patterns in different states were compensated. Furthermore, the German health insurance company BARMER identified high prescribing practices in Hessen and Westphalia and invited the top 13.8% of the PPI prescribing practices to participate in our study. At least 10 out of 143 study practices were high prescribers. The sample of practices was thus highly generalizable. Although this was a cluster-randomized study, relevant characteristics of participating patients and practices were well balanced between study arms.For studies of this kind, practices interested in the topic are easier to motivate to take part. Since these have often reflected on their prescribing behavior, ceiling effects may result. Despite this, the implementation of arriba-PPI was effective at T1.Between the 6th and 12th month of data collection, there was also a decrease in PPI prescriptions in the control group, so that the difference between the intervention and control group was no longer significant at the end of the data collection period. Measures in the health care system were introduced to reduce PPI prescribing. This included not only information on risks and cost, but also threatened prescribing GPs with monetary sanctions for inappropriate prescribing. This could have resulted in a more conscious way to prescribe PPI.We also cannot exclude a certain degree of contamination. The patient interview at 6 months may have influenced the control group’s attitude toward PPI use. As there was no consultation planned in this group, the phone interview was the only conversation for these patients concerning their medication. Also there could be a certain degree of social desirability bias when patients were directly asked about their PPI uptake. Lastly, interviewers were not blinded.