A blood pressure (BP) difference between arms was first reported over 100 years ago. Knowledge of its prevalence and relevance to the accurate measurement of BP remains poor. Current hypertension guidelines do not emphasise it. The objectives of this study were to establish the best estimate of prevalence of the interarm difference (IAD) in the population, to consider its implications for accurate BP measurement and treatment, and to discuss its aetiology and potential as a risk marker for cardiovascular disease. Systematic literature review was carried out. The data sources were Medline EMBASE and CINAHL databases, and Index of Theses. Studies reporting prevalence rates of IAD were retrieved and considered for inclusion against explicit methodological criteria. Point prevalence rates were extracted and weighted mean prevalence rates calculated. The main outcome measures were weighted mean prevalences of systolic IADX10 and X20 mm Hg and of diastolic IADX10 mm Hg. Thirty-one studies were identified. Most had methodological weaknesses; only four met the inclusion criteria. Pooled prevalences of the IAD from these four studies were 19.6% systolic X10 mm Hg (95% CI 18.0-21.3%), 4.2% systolic X20 mm Hg (95% CI 3.4-5.1%) and 8.1% diastolic X10 mm Hg (95%CI 6.9-9.2%). In conclusion, an IAD is present in a substantial number of patients and should be looked for whenever diagnosis and treatment depend on accurate measurements of BP. The importance of an IAD should be better emphasised in current hypertension management guidelines. There is evidence associating an IAD with peripheral vascular disease, raising the possibility that its presence may predict cardiovascular events.
IntroductionPatients are regularly encountered in the clinical setting with a different systolic or diastolic blood pressure (BP) in each arm. Comparisons of arm pressures have been made ever since the modern sphygmomanometer was introduced, 1 yet the significance of this finding, which Cyriax named the 'differential BP sign', 2 is still poorly appreciated today.Hypertension is one of the major causes of premature morbidity and mortality throughout the developed and developing worlds. 3 The vast majority of patients with hypertension are managed in primary care 4 and measurement of BP is the most common investigation performed in this setting. 5 The management of hypertension is known to be suboptimal; 6 therefore, knowledge of the latest guidelines, and the many factors known to influence readings, is crucial. 7 The prevalence of a systolic (sIAD) or a diastolic (dIAD) inter-arm difference, its importance for the management of hypertension, its significance as a potential marker of peripheral vascular disease (PVD) and predictor of cardiovascular disease (CVD) in hypertensive patients are the subjects of this review.Although recent ambulatory BP monitoring guidelines recommend routine bilateral assessment, 8 the latest British guidelines for the management of hypertension merely state that 'BP should initially be measured in both arms as patient...