Implications of Inaccurate Blood Pressure Measurement on Hypertension Prevalence.

Background: The cornerstone of the management of hypertension is accurate measurement of blood pressure (BP). A recent study showed that more than one-half of home BP devices sold in Canada have no evidence of validation for accuracy. The purpose of this study was to model the implications of inaccurate BP measurements on diagnosis and control of hypertension. Methods: We used data from the Canadian Health Measures Survey to model the effects of inaccurate BP devices by 5 or 10 mm Hg over or under the true BP value. Hypertension was defined as BP ≥ 140/90 mm Hg (or ≥130/80 mm Hg in those patients with diabetes). Results: If both systolic and diastolic BP were overestimated by 10 mm Hg, the prevalence of hypertension would falsely increase by 50% to 63%, potentially leading to overtreatment of approximately 3.5 million Canadians. Conversely, the impact of underestimation of BP appeared minimal, but mostly because of design limitations of our study. Conclusions: We found that overestimation of BP by only 10 mm Hg could lead to overtreatment of up to 3.5 million Canadians. Government should mandate the validation of BP devices before they can be sold; until then, clinicians and patients should be cautious in their selection of BP devices, using the Hypertension Canada Recommended Device Program to guide selection.