Blood pressure measurement method and inter-arm differences: A meta-analysis

Abstract

Background Screening for inter-arm difference (IAD) of blood pressure (BP) at each first visit is recommended by numerous guidelines whereas it is unclear whether the method by which IAD is measured has significant influence on the IAD value. Methods A systematic review is made of the studies reporting on double-arm measurements and the association of IAD with procedure characteristics (Medline/PubMed, Embase, and Cochrane Library). Results The mean absolute IAD was 5.4 ± 1.7 and 3.6 ± 1.2mmHg for systolic and diastolic BP, respectively. Of all subjects 14% had a systolic IAD ≥ 10mmHg, 4% a systolic IAD ≥ 20mmHg, and 7% a diastolic IAD ≥ 10mmHg. The relative risk (RR) of obtaining a systolic IAD 10 and ≥ 20mmHg and a diastolic IAD ≥ 10mmHg is higher when measuring sequentially instead of simultaneously (2.2 (95% CI: 1.4-3.6), P < 0.01; 4.8 (95% CI: 1.1-21.9), P < 0.05 and 2.5 (95% CI: 1.0-6.3) P < 0.05, respectively), when using a manual instead of an automated device (2.1 (95% CI: 1.1-3.9), P < 0.05; 4.4 (95% CI: 1.8-10.8), P < 0.01 and 3.7 (95% CI: 1.6-8.6), P < 0.01, respectively) and when performing only one BP measurement instead of multiple (2.0 (95% CI: 1.1-3.8), P < 0.05; 4.3 (95% CI: 1.6-11.4), P < 0.01 and 4.4 (95% CI: 1.7-11.4), P < 0.01, respectively). Conclusions creening for IAD of BP is important but the measurement methodology has a major influence on IAD results. To prevent overestimation and observer bias IAD should be assessed simultaneously at both arms, with one or two automatic devices and multiple readings should be taken. © 2011 American Journal of Hypertension, Ltd.