Clinical Methods and PharmacologyEffects of systematic errors in blood pressure measurements on the diagnosis of hypertensionTurner, Martin J.a; Baker, A. Barrya; Kam, Peter C.bAuthor Information aDepartment of Anaesthetics, University of Sydney, Royal Prince Alfred Hospital, Sydney bDepartment of Anaesthetics, Emergency Medicine & Intensive Care, University of New South Wales, Sydney, New South Wales, Australia Correspondence and requests for reprints to Dr M. J. Turner, Department of Anaesthesia, Royal Prince Alfred Hospital, Building 89 Level 4, Missenden Rd, Camperdown, NSW 2050, Australia Tel: +61 2 9515 8591/8733; fax: +61 2 9519 2455; e-mail: [email protected] Received 18 May 2004 Revised 20 July 2004 Accepted 30 July 2004 Blood Pressure Monitoring: October 2004 - Volume 9 - Issue 5 - p 249-253 Buy Abstract Objective To estimate the effects of systematic errors in measurements of blood pressure on the diagnosis of hypertension. Methods We fitted regression curves to distributions of diastolic and systolic BP from recent Canadian and UK surveys and calculated the effect of systematic measurement errors on changes in the numbers of patients who would be classified hypertensive at thresholds of 85, 90 and 95 mmHg diastolic and 140 and 160 mmHg systolic pressure respectively. Results Overestimation of diastolic BP by 5 mmHg increases the number of patients whose diastolic BP exceeds 85, 90 and 95 mmHg by 102, 132 and 166% respectively. Equivalent underestimation causes 57, 62 and 67% respectively of hypertensive patients to be missed. If systematic error in diastolic pressure is limited to ±1 mmHg the diagnosis errors are between −15 and +23%. Overestimation of systolic BP by 3 and 5 mmHg increases the number classified as hypertensive by 24 and 43% respectively. Equivalent underestimation causes 19 and 30% of patients with systolic hypertension to be missed. Conclusions Small systematic errors in BP measurements may cause large variations in the proportion of patients diagnosed as hypertensive. To limit over- or under-diagnosis of diastolic hypertension to approximately 20%, systematic errors in diastolic BP measurements should be limited to 1 mmHg. An uncertainty of 3 mmHg may be adequate for detecting systolic hypertension. © 2004 Lippincott Williams & Wilkins, Inc.