Determinants of variability in repeated auscultatory blood pressure measurements

OBJECTIVE: Auscultation is the reference standard for validating automated blood pressure monitoring. However, its inherent variability may compromise validation reliability. This study aimed to quantify the variability in repeated auscultatory measurements and determine the relative contributions of the underlying factors. METHODS: Data were analyzed from an accuracy validation study ( n = 85) conducted under the International Organization for Standardization 81060-2 : 2018+Amd 1 : 2020 standard, wherein two trained observers performed simultaneous auscultatory measurements. Using the Guide to the Expression of Uncertainty in Measurement framework, the total variability of repeated auscultatory measurements was decomposed into the proportional contributions of the blood pressure determination methodology (inherent uncertainty of identifying Korotkoff sounds during cuff deflation), observer, and participant. RESULTS: A total of 85 participants (55.3% female), including 13 receiving antihypertensive medications, were analyzed. The mean age was 59.5 ± 10.2 years. Mean systolic/diastolic blood pressure were 124.9 ± 24.1/76.5 ± 14.2 mmHg. Repeated auscultatory measurements showed variability with SDs of 4.91 mmHg for systolic and 3.26 mmHg for diastolic blood pressure ( n = 255). The analysis identified methodology as the largest contributor to variability (systolic: 47.4%, diastolic: 46.0%), while observer and participant factors contributed less (systolic: 5.3% and 7.1%; diastolic: 16.4% and 6.8%). CONCLUSION: Substantial variability exists in auscultatory blood pressure measurements, even when performed under the International Organization for Standardization standard, with the determination methodology being the primary source. Our findings suggest that the inherent variability of the auscultatory method should be acknowledged as a limiting factor in identifying accurate blood pressure in clinical and research settings.