In cluster randomised trials (CRT), groups (rather than individuals) are randomised to intervention and control conditions. Since the publication of the Ottawa Statement on the Ethical Design and Conduct of CRTs, the accurate identification of research participants has continued to challenge researchers and research ethics committees.

In this article, we focus on CRTs involving healthcare providers and provide a practical framework for applying Ottawa Statement criteria for identifying research participants. We illustrate key lessons with example CRTs.

Study procedures should be analysed in relation to the study objective. A study intervention confers research participant status on healthcare providers if the study objective is to evaluate its effect and it is delivered to or targeted at healthcare providers. A data collection procedure confers research participant status on healthcare providers if it informs a study outcome used to achieve the study objective and it involves interactions between researchers and healthcare providers to collect their data, or the collection of healthcare providers’ identifiable private information.

In CRTs, healthcare providers may be research participants because of study interventions, data collection procedures, or both; conversely, they may simply be research collaborators. Some study interventions confer research participant status on both healthcare providers and patients. Collecting data on healthcare provider behaviour may confer research participant status on healthcare providers.

Accurately identifying research participants in CRTs is essential to their ethical conduct. When healthcare providers are research participants, their rights and welfare should be protected in accordance with research ethics guidelines.

Cardiovascular events (CVEs), in particular acute coronary syndrome (ACS), complicate the course of a significant number of patients hospitalised for community-acquired pneumonia (CAP) or influenza. Emerging evidence suggests that this increased risk of CVEs could be mitigated by the use of acetylsalicylic acid (aspirin). The ASCAP study investigates whether the addition of aspirin to standard therapy in hospitalised patients with moderate-to-severe CAP or influenza can reduce the incidence of CVEs.

The ASCAP study is a multicentre, double-blind, placebo-controlled randomised trial in 16 university and general hospitals in the Netherlands, in which patients are randomised to acetylsalicylic acid or matching placebo for 90 days. Eligible patients are adults hospitalised for moderate-to-severe CAP or influenza. Patients with antithrombotic or anticoagulant drugs, or those with contraindications for aspirin, are excluded. The primary outcome is the incidence of ACS up to day 180. Secondary outcomes include the incidence of 4-point major adverse cardiovascular events up to day 180, as well as the incidence of major bleeding and clinically relevant non-major bleeding events up to day 90, all-cause mortality up to day 180 and quality of life and societal costs up to day 180. Survival time will be analysed by the log-rank test, stratified for CAP and influenza, with a two-sided alpha of 0.05. Assuming an average baseline ACS risk of 7.5% over 180 days with up to 30% variation across strata, and a 60% hazard reduction due to aspirin, the required sample size to achieve 80% power is 760 patients. Currently, 114 patients are enrolled in the study.

This study is approved by the Medical Ethics Committee Amsterdam UMC (Amsterdam, The Netherlands) under reference number 2023.0741 and registered under EU trial number 2023-504553-12-01 in the EU portal CTIS (Clinical Trials Information System). Results of the study will be published in a peer-reviewed journal.

EU CTIS: 2023-504553-12-01.