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Seeing is believing: blinding practices during point-of-care ultrasound research

Blog entry written on: Blinding practices during acute point-of-care ultrasound research: the BLIND-US meta-research study, (bmjebm-2020-111577)

Authors: Ross Prager, Kay Wu2, Roudi Bachar, Rudy R Unni, Joshua Bowdridge, Trevor A McGrath, Rajiv Thavanathan, Michael Y Woo, Matthew D F McInnes

Point of care ultrasound (POCUS) has become an invaluable tool for many clinicians. As the evidence supporting its integration into clinical practice grows, a critical look at research practices is important to ensure decisions are being made with the highest quality evidence possible.

One aspect of diagnostic accuracy study design that may impact generalizability and risk of bias are blinding practices. Whereas blinding of the POCUS interpreter to the reference stands (and vice versa) is as an important step to limit bias, whether the person performing the POCUS scan should be blinded to the patient’s clinical information is less clear. The objective of our study was to characterize blinding practices during acute POCUS research.

In our study “Blinding practices during acute point-of-care ultrasound research: the BLIND-US meta-research study” (bmjebm-2020-111577), we searched the acute POCUS literature for studies assessing the diagnostic accuracy of POCUS. We identified 97 studies meeting the inclusion criteria. We found that the POCUS interpreter was blinded to clinical information in 37 studies (38.1%), not blinded in 34 studies (35.1%), and not reported in 26 studies (26.8%). The POCUS interpreter was the same person obtaining the images in 72 studies (74.2%), different in 14 studies (14.4%), and not reported in 11 studies (11.3%).

This significant variation in blinding practices is important to discuss. We would argue that blinding the POCUS interpreter to clinical information places the test outside of its routine clinical use. This may limit generalizability, applicability, and ultimately accurate translation of research into practice. This means that for clinicians reading POCUS studies, attention to the blinding practices is important to ensure the results are generalizable. For researchers designing POCUS studies, we recommend that POCUS interpreters not be blinded to the clinical information, as blinding to clinical information is not reflective of the routine clinical use of POCUS. Additionally, researchers should consider reporting incremental diagnostic yield (how much additional accuracy a test provides in an existing diagnostic pathway) or assessing other patient centered outcomes. These study designs move beyond the question of whether POCUS can be performed, to whether POCUS should be performed for a specific indication.

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Ross Prager, MD
Internal Medicine Resident
University of Ottawa

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Ross Prager has no conflict of interest to declare


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