Sixty seconds on . . . measuring blood pressureBMJ 2016; 353 doi: https://doi.org/10.1136/bmj.i2626 (Published 10 May 2016) Cite this as: BMJ 2016;353:i2626
Eh? Don’t we all know how to measure blood pressure? Even patients do it these days
You may think you’re doing it right, but are you taking measurements from both arms?
The recommendation came in NICE guidance CG34, issued in 2006. A 2007 study by Carl Heneghan and colleagues of Oxford’s Centre for Evidence-Based Medicine found that although 77% of GPs were aware of the guidance, only 30% agreed with it and even fewer, 13%, actually followed it.1
Not especially. Guidance isn’t holy writ. But there’s growing evidence that this particular injunction ought to be followed more widely.
A new study led by Christopher Clark of the University of Exeter Medical School found that in healthy people with no pre-existing clinical cardiovascular disease a difference of as little as 5 mm Hg in systolic blood pressure between the right and left arm was linked to an increase in the risk of cardiovascular death within 10 years (adjusted hazard ratio 1.44 (95% confidence interval 1.15 to 1.79)).2
Previous studies have shown associations in people with pre-existing disease. And the NICE guidance says that a difference of 10 mm Hg may be considered normal, that 15 mm Hg “may indicate increased risk of vascular disease and that 20 mm Hg warrants specialist investigation.” So the new work backs the guidance and indicates that even smaller arm differences between the arms may be important.
Any weakness in the findings?
They aren’t wholly consistent—that is, there isn’t a clear dose-response relation. And the prevalence of inter-arm differences is high: 60% of the 2400 people in the study showed a difference of 5 mm Hg or more. This was probably because blood pressure was measured just once, one arm after the other, and not repeated. Simultaneous, automated, and repeated measurements might show a lower prevalence, the authors say.
Will this finding change the guidance?
It might. A review of NICE’s guidance is due in June.