Effect of Peer Comparison Feedback and Professional Norms on Vitamin D Testing and Generic Medication Prescribing.

Authors

Tobias Müller, Michael Gerfin, Raf Van Gestel

Published in

NEJM evidence. Volume 5. Issue 9. Pages EVIDoa2400308. Epub Aug 25, 2026.

Abstract

Organization for Economic Cooperation and Development (OECD) estimates suggest that 20% of health care spending is wasteful or even harmful. Previous interventions have had limited success in discouraging low-value care in medical practice.
We conducted a nationwide randomized controlled trial among primary care physicians (PCPs) in Switzerland (November 2020-December 2021). We randomly assigned PCPs to one of three intervention groups related to low-value care (vitamin D testing, generic prescribing, or a cost intervention) or a control group. This article reports results for the vitamin D testing and generic prescribing interventions compared with the common control group. PCPs in the intervention groups received a personalized information letter combining professional norms and peer comparison feedback about the low-value service (either vitamin D testing or prescribing of nongeneric medications). Primary endpoints were (1) the number of vitamin D tests per 100 patients and (2) the share of generic medications prescribed. We estimated average treatment effects using linear regression and assessed effect heterogeneity with a causal forest.
A total of 618 PCPs were randomly assigned to the vitamin D intervention, 597 to the generic prescribing intervention and 601 to the common control group. The intervention reduced average vitamin D testing by 3.66 tests per 100 patients (95% confidence interval [CI], -5.42 to -1.89; P<0.001). The intervention did not increase average generic medication prescribing (mean difference, +0.57 percentage points; 95% CI, -0.68 to +1.81 percentage points; P=0.37). Heterogeneity analysis suggested that reductions in vitamin D testing among physician subgroups ranged from one to seven per 100 patients and that higher baseline generic prescribing rates were associated with increases in generic substitution following the intervention. No increases in low-value care were seen among those physicians with low baseline levels.
Peer comparison letters emphasizing professional norms reduced vitamin D testing but did not increase generic medication prescribing. (Funded by the Swiss National Science Foundation; AEA Randomized Controlled Trials Registry no., AEARCTR-0004747.).

PMID:
42640164
Bibliographic data and abstract were imported from PubMed on 25 Aug 2026.

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