All you need to read in the other general journalsBMJ 2011; 342 doi: https://doi.org/10.1136/bmj.d4015 (Published 29 June 2011) Cite this as: BMJ 2011;342:d4015
Technique matters when measuring blood pressure
Biological variation in blood pressure and random measurement errors mean that doctors and researchers often have to second guess a patient’s true blood pressure from a moving target. Readings from the same person fluctuate from hour to hour, from day to day, and from place to place. Health professionals know they should base treatment decisions on averages from a series of readings, but repeat visits are time consuming and inconvenient for everyone. Averaging measurements taken at home may be the answer, say researchers. In their study of 444 hypertensive men, within person variance fell sharply with increasing number of measurements, and the effect was the same at home, in the clinic, or in a research setting. The authors write that patients can be 80% certain of their true systolic blood pressure after five home readings. The cost of monitors should be reimbursed by insurers or the state.
This study, along with many others, confirms that readings taken in clinics are higher than readings taken at home. “White coat” effects are well known, but a linked commentary (pp 838-9) also blames poor training, poor oversight, and “remarkably casual” technique—cuffs applied over clothes, hurried patients slumped over desks, old equipment allowed to drift from its original calibration. Clear guidance about how to do it better, including multiple readings, has been around since 1939 and largely ignored. It’s time to add measurement technique to quality assurance standards, say the commentary’s authors. Only then will we begin to take measuring blood pressure seriously.