Defining the relationship between arm and leg blood pressure readings: a systematic review and meta-analysis

Objectives: To define the relationship between arm and leg blood pressure to inform the interpretation of leg blood pressure readings in routine clinical practice where arm readings are not available.

Methods: Systematic review of all existing studies comparing arm and leg blood pressure measurements. A search strategy was designed in MEDLINE and adapted to be run across six further databases. Articles were deemed eligible for inclusion if they measured and reported arm and leg blood pressure taken in the supine position and/or the difference between the two. Mean values for arm-leg blood pressure difference and measures of precision (95% confidence intervals [CI] or standard deviation) were extracted and entered into a random-effects meta-analysis.

Results: A total of 887 articles were screened and 44 were included in the descriptive analyses, including 9,771 patients. In the general population, ankle systolic blood pressure was 17.0 mmHg (95%CI 15.4 to 21.3 mmHg) higher than arm blood pressure in the supine position. For diastolic blood pressure, there was no difference between arm and ankle blood pressure (-0.3 mmHg, 95%CI -1.5 to 1.0 mmHg). In patients with vascular disease, systolic blood pressure was -33.3 mmHg (95%CI -59.1 to -7.6 mmHg) lower in the ankle compared to the arm.

Conclusions: This is the first review to provide empirical data defining the difference between blood pressure in the arm and leg in the general population. Findings suggest a diagnostic threshold of 155/90 mmHg could be used for diagnosing hypertension when only ankle measurements are available in routine
practice.