Clinical Question

What is the best way to measure blood pressure?

Bottom Line

To get the most accurate measure, let patients sit for a few minutes, and then measure their blood pressure on a completely bare arm. Does a difference of 4 mm systolic and 6 to 7 mm diastolic matter? It might, especially when deciding whether to add a second or third drug. Also, remember to confirm office-based blood pressures with an out-of-office measurement (either ambulatory blood pressure monitoring or home blood pressure measurements), because many patients have white coat hypertension. (Level of Evidence = 2c)

Synopsis

It is important that we measure blood pressure in our offices in the same way it is done in studies of hypertension diagnosis and treatment. Otherwise, we risk misclassifying patients and may overtreat or undertreat them. This simple cross-sectional study recruited 186 adults in a Japanese primary care clinic and in two adult day care facilities. Blood pressure was measured using an automated cuff in three conditions: a completely bare arm, an arm covered by a sleeve no more than 1 mm thick to the wrist (a cardigan with a 1-mm thick sleeve was provided, if necessary), or an arm with the sleeve rolled up over the elbow. All patients were first asked to sit in a chair for five minutes before the measurement, with their arm supported and level. The researchers systematically varied the order in which blood pressure was measured. For each condition, the final blood pressure was the average of three measurements. The participants had a mean age of 75 years, 62% were female, and approximately 63% had hypertension. The mean blood pressures were 129/67 mm Hg taken on a bare arm, 133/73 mm Hg on a fully sleeved arm, and 133/74 mm Hg on an arm with the rolled-up sleeve. The difference persisted after adjusting for age and measurement order in an analysis of variance model. It is also interesting that the mean blood pressure decreased from the first measurement (135/74 mm Hg) to the second measurement (131/71 mm Hg) and to the third measurement (129/70 mm Hg).

Study design: Cross-sectional

Funding source: Self-funded or unfunded

Setting: Outpatient (primary care)

Reference: Ozone S, Shaku F, Sato M, Takayashiki A, Tsutsumi M, Maeno T. Comparison of blood pressure measurements on the bare arm, over a sleeve and over a rolled-up sleeve in the elderly. Fam Pract. 2016;33(5):517-522.