Inter-arm blood pressure difference and cardiovascular risk estimation in primary care: a pilot study.

Background: Systolic inter-arm differences (IAD) in blood pressure (BP) contribute independently to cardiovascular risk estimates. This can be used to refine predicted risk and guide personalised interventions.

Aim: To model the effect of accounting for IAD in cardiovascular risk estimation in a primary care population free of pre-existing cardiovascular disease.

Design & Setting: A cross-sectional analysis of people aged 40-75 years attending NHS Health Checks in one general practice in England.

Method: Simultaneous bilateral BP measurements were made during health checks. QRISK2, atherosclerotic cardiovascular disease (ASCVD), and Framingham cardiovascular risk scores were calculated before and after adjustment for IAD using previously published hazard ratios. Reclassification across guideline-recommended intervention thresholds was analysed.

Results: Data for 334 participants were analysed. Mean (standard deviation) QRISK2, ASCVD, and Framingham scores were 8.0 (6.9), 6.9 (6.5), and 10.7 (8.1), respectively, rising to 8.9 (7.7), 7.1 (6.7), and 11.2 (8.5) after adjustment for IAD. Thirteen (3.9%) participants were reclassified from below to above the 10% QRISK2 threshold, three (0.9%) for the ASCVD 10% threshold, and nine (2.7%) for the Framingham 15% threshold.

Conclusion: Knowledge of IAD can be used to refine cardiovascular risk estimates in primary care. By accounting for IAD, recommendations of interventions for primary prevention of cardiovascular disease can be personalised and treatment offered to those at greater than average risk. When assessing elevated clinic BP readings, both arms should be measured to allow fuller estimation of cardiovascular risk.