Re: Accurate measurement of blood pressure

Issue: BCMJ, vol. 54, No. 10, December 2012, Page 491 Letters

I was somewhat surprised that the authors of the otherwise comprehensive articles on hypertension in the October 2012 BCMJ [“Assessing and managing hypertension” 54:390-412] did not take the opportunity to remind us of the existence of inter-arm dif­ference in blood pressure and its significance. The 2012 Canadian Hypertension Education Program (CHEP) recommendations state, “For initial read­ings, take the blood pressure in both arms and subsequently measure it in the arm with the highest reading.” Failure to follow these recommendations can delay the diagnosis of hypertension.

Inter-arm difference is relatively common. In a study of 230 people re­ceiving treatment for hypertension in primary care, Clark and colleagues found that 24% of people being treated for hypertension had a mean inter-arm difference in systolic blood pressure of 10 mm Hg or more and 9% of 15 mm Hg or more.[1]

Are such differences of clinical significance? Clark and colleagues think so. In their meta-analysis of 20 studies, they found that a difference of 10 mm Hg or more was strongly associated with subclavian stenosis and that a difference of 15 mm Hg or more was associated with peripheral vascular disease. 

They conclude that a difference of 10 mm Hg, or of 15 mm Hg or more between arms might help to identify patients who need further vascular assessment.[2]

Unfortunately, pharmacies with blood pressure measuring stations are set up so that it is virtually impossible to use the right arm for measurement.

Even in primary care, bilateral blood pressure measurements are not routine, probably for similar ergo­nomic reasons.

Although some physicians may be deterred by reading that simultaneous rather than sequential measurements are required, this is not practical—nor is it required by CHEP guidelines.
—Colin Campin, MB
Salt Spring Island


1.    Clark CE, Taylor RS, Shore AC, et al. The difference in blood pressure readings between arms and survival: Primary care cohort study. BMJ 2012;344:e1327.
2.    Clark CE, Taylor RS, Shore AC, et al. Association of a difference in systolic blood pressure between arms with vascular disease and mortality: A systematic review and meta-analysis. Lancet 2012;379(9819):905-914.

Colin Campin, MB,. Re: Accurate measurement of blood pressure. BCMJ, Vol. 54, No. 10, December, 2012, Page(s) 491 - Letters.

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