Impact of inter-arm blood pressure difference on cardiovascular risk estimation in primary care

Objective: The Inter-arm blood Pressure difference Individual Patient Data (INTERPRESS-IPD) Collaboration recently demonstrated, based on data from over 57,000 records, that an inter-arm difference in systolic blood pressure (IAD) is an independent risk marker for cardiovascular events after adjustment for Framingham or QRISK2 scores. This approach offers improved risk prediction through reclassification of individuals across risk categories and can result in initiation of treatment for primary prevention of cardiovascular disease in those close to current pharmaceutical intervention thresholds. The aim of this study was to model this approach of adjusting cardiovascular risk prediction scores for IAD in a typical primary care population.

Design and method: Individuals aged 45–75 years, free of cardiovascular disease, had bilateral blood pressure measured three times, simultaneously, during National Health Service (NHS) Health Checks in one rural general practice in Devon, England. QRISK2 scores were calculated as part of the Health Check process, Framingham risk scores were calculated during analysis with Stata v15.0. Framingham and QRISK2 risk scores were adjusted by taking account of hazard ratios for IAD derived from our INTERPRESS-IPD analyses.

Results: Complete data existed for 334 participants [mean (standard deviation): age 57.4 (9.3), systolic/diastolic blood pressure 132 (14)/79 (8.5)]. Mean Framingham and QRISK2 scores were 10.7 (8.1) and 8.0 (6.9), respectively before adjustment for IAD, and 11.1 (8.5) and 8.2 (7.1) afterwards (see figure). Overall, 10 (3%) participants were reclassified from below to above either the 10% or 20% Framingham risk thresholds, and 2 (1%) individuals were reclassified across the corresponding QRISK2 thresholds. For individuals with initial risk scores of 8% to 9.9%, 7/38 (18%) were reclassified to a Framingham risk above 10% and 2/35 (6%) to a QRISK2 score above 10%.

Conclusions: Our findings confirm that systolic IADs can be applied to refine cardiovascular risk estimates in a UK primary care population. By taking account of systolic IAD, individual decisions on interventions for primary prevention of cardiovascular disease can be personalised, and could facilitate targeting of treatment to those at greater than average cardiovascular risk.