In this RCT, the only biological outcome reported as statistically significant was systolic blood pressure. Blood pressure is inherently difficult to measure accurately and, without blinding of participants or assessors, is susceptible to bias.

On reviewing the protocol paper (JMIR Res Protoc 2021;10(5):e28684) and the outcomes paper, I noticed an unacknowledged deviation in the measurement method:

Protocol: “Blood pressure is measured using the Dinamap or Accutor 7 or Dinamap V100 blood pressure monitor after participants have rested while seated for at least 5 minutes. Measures are taken at least three times, and the mean of the second and third readings will be calculated.”

Outcomes paper: “Resting blood pressure was measured using the Dinamap/Accutor 7 or Dinamap V100 blood pressure monitor after participants had rested while seated for ≥5 minutes. Blood pressure was measured 3 or 4 times, and the mean of all available measures was used.”

The change from using the mean of the second and third readings to the mean of all available readings is not explained. This raises questions about the rationale for the change, whether it was made before unblinding, and whether it could have influenced the result.

Given that this is the key reported biological effect in a trial that otherwise found minimal impact on other outcomes, clarification from the authors about this methodological change and its timing would be valuable. What else from the protocol paper has also not been adhered to and why?