Comparative effectiveness research considered methodological insights from simulation studies in physician’s prescribing preference

Objective: To review comparative effectiveness research (CER) using physician’s prescribing preference as an instrumental variable (PPP IV) in pharmacoepidemiology, and to review methodological studies that use simulation to evaluate the performance PPP IV in CER. Study design and setting: We conducted a review of CER using PPP IV as well as studies evaluating the use of PPP IV by using simulation methods. We searched Ovid, PubMed, and Google Scholar databases from 2005 to 2020. Results: We identified 6 simulation studies and 18 CER studies. The simulation studies explored the most suitable ways for using PPP IV in different settings (outcome types, sample size, the prevalence of outcomes) which can be useful guidance for using PPP IV in CER. The CERs studies identified show heterogeneity in terms of validation assumptions, estimation methods and sample size. Not all applied studies utilised the methodological insights from the simulation studies. However, they all concluded that PPP is a valid instrumental variable. Conclusion: Future CER should consider a range of methodological issues to improve the validity of findings when using PPP IV. Specifically, studies should consider the impact of different choice of statistical methods, forms of proxy for measuring preference, time-varying exposures, and the type of outcome.