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Effectiveness of the IQM peer review procedure to improve in-patient care—a pragmatic cluster randomized controlled trial (IMPRESS): study design and baseline results



The primary objective of the IMPRESS study is to assess the causal effects of the IQM peer review on mortality in patients ventilated > 24 h. Secondary analyses are conducted for mortality in patients with myocardial infarction, stroke, COPD, pneumonia, and the procedural provision of a colorectal resection. This article provides a description of the study design and presents baseline results.

Subjects and methods

Descriptive statistics for 231 included hospitals and patient characteristics.


Due to randomization, the treatment/control group hospitals were similar with respect to the mortality in patients ventilated > 24 h and other patient and hospital characteristics at baseline. Mortality was highest (lowest) in patients ventilated > 24 h (with colorectal resection).


The IMPRESS study provides a unique opportunity to assess the impact of the IQM peer review on the mortality in patients ventilated > 24 h. The secondary, exploratory, and qualitative analyses are expected to provide insights on determinants of in-hospital mortality, structure and process quality, and the robustness of different approaches to risk adjustment of quality indicators.

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The authors are grateful for the support of Dr. Claudia Winkelmair and the IQM office. We also thank the participating IQM hospitals and the peer reviewers.


The IMPRESS study is funded by the Innovation Fund of the Joint Federal Committee (Gemeinsamer Bundesausschuss, G-BA), Germany. Funding number: 01VSF16013.

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Correspondence to Martin Roessler.

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Conflict of interest

Peter C. Scriba and Ralf Kuhlen are members of the scientific advisory board of the Initiative Qualitätsmedizin e.V. (IQM). Maria Eberlein-Gonska serves as an external expert for IQM. The other authors declare that they have no conflict of interest.

Ethics approval and consent to participate

The study was approved by the ethics committee of the TU Dresden. Written consent of participation was obtained from all included IQM member hospitals.

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Schmitt, J., Schoffer, O., Walther, F. et al. Effectiveness of the IQM peer review procedure to improve in-patient care—a pragmatic cluster randomized controlled trial (IMPRESS): study design and baseline results. J Public Health (Berl.) 29, 195–203 (2021).

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  • Peer review
  • Ventilation
  • Hospital mortality
  • Cluster-randomized controlled trial