Exeter, UK—Guidelines urge measuring BP in both arms, but the advice is often ignored.

A new UK study from the University of Exeter urged that BP be measured in both arms, and the higher reading should be recorded. The researchers report in the journal Hyptertension that the method improves hypertension diagnosis and management.

The study team analyzed data from 53,172 participants in 23 studies worldwide to reach their conclusions. The researchers determined that using the higher arm BP reading reclassified 12% of patients as having hypertension; if the lower ready arm had been used, they would have fallen below the threshold for diagnosis.

"High blood pressure is a global issue, and poor management can be fatal," stated lead author Christopher Clark, MB ChB, MSc, PhD. "This study shows that failure to measure both arms and use the higher reading arm will not only result in underdiagnosis and undertreatment of high blood pressure but also underestimation of cardiovascular risks for millions of people worldwide."

The background information in the article noted that guidelines recommend measuring BP in both arms, adopting the higher arm readings for diagnosis and management.

It often has not been followed, the authors pointed out, and data to support this recommendation are lacking. That led researchers to evaluate associations of higher and lower arm systolic BPs with diagnostic and treatment thresholds and prognosis in hypertension, using data from the Inter-arm Blood Pressure Difference—Individual Participant Data Collaboration.

The focus was on associations of higher or lower reading arm BPs with cardiovascular mortality, all-cause mortality, and cardiovascular events in individual participant data meta-analyses pooled from 23 cohorts. Cardiovascular events were modelled for Framingham and atherosclerotic cardiovascular disease risk scores. Overall, 53,172 participants (mean age 60 years; 48% female) were included.

The results indicated that higher arm BP, compared with lower arm, reclassified 12% of participants at either 130- or 140-mmHg systolic BP thresholds (both P <.001). "Higher arm BP models fitted better for all-cause mortality, cardiovascular mortality, and cardiovascular events (all P <.001)," the researchers advised. "Higher arm BP models better predicted cardiovascular events with Framingham and atherosclerotic cardiovascular disease risk scores (both P <.001) and reclassified 4.6% and 3.5% of participants respectively to higher risk categories compared with lower arm BPs."

The authors concluded, "All prediction models performed better when using the higher arm BP. Both arms should be measured for accurate diagnosis and management of hypertension."

"It's impossible to predict the best arm for blood pressure measurement as some people have a higher reading in their left arm compared to right and equal numbers have the opposite," Dr. Clark stated. "Therefore, it's important to check both arms as detecting high blood pressure correctly is a vital step towards giving the right treatment to the right people." He also added, "Our study now provides the first evidence that the higher reading arm blood pressure is the better predictor of future cardiovascular risk."

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