Take BP readings on both arms

Measuring blood pressure in both arms could uncover undetected hypertension, research suggests.

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Measuring blood pressure in both arms could diagnose more cases of hypertension and trigger more intensive treatment in around 10% of patients who already have the diagnosis. 

Identifying patients with more than 10mmHg difference in interarm blood pressure readings would result in 10% of people having their hypertension status reclassified to a higher level, the WONCA conference in Sydney heard last month. 

Family medicine physician Professor Oswald Peter Adams determined from a quick straw poll of the GP audience that most GPs did not measure blood pressure in both arms on a patient’s initial visit. 

Whether the reason was a lack of awareness of the guideline or simply a lack of adherence, the fact was that taking BP in both arms was not a common practice, said the dean of the faculty of medical sciences at The University of the West Indies. 

However, interarm pressure differences of more than 10 mmHg helped identify patients needing further vascular assessment, Professor Adams told the conference. 

Taking readings of both arms would move “a considerable number of people, 12% in some studies, over the hypertension diagnosis control threshold,” he said. 

“Diagnosis and management decisions may be affected in roughly 10% of patients using the higher versus lower arm reading.  

“Large differences in interarm pressures may identify patients needing further vascular assessment.” 

Professor Adams presented research on 2900 adults aged over 40 from four Caribbean islands, 40% of whom were on antihypertensive medication 

Researchers measured blood pressure in both arms of each patient after they’d been seated for five minutes, and did three readings, one minute apart. 

The study found 10% of all participants had an interarm pressure difference of greater than 10mmHg. Researchers determined that of these patients with the highest interarm pressure, one in 11 would have their 10-year and atherosclerotic cardiovascular risk increase from less than 10% to greater than 10%. 

In addition, the study found that 37% of participants had at least a 5mmHg interarm difference. 

In Australia, guidelines state that if the difference in blood pressure between arms is greater than 5mmHg, the higher reading should be used. 

“Measuring BP in both arms is simple and helps refine risk assessment and is certainly simpler than a risk assessment using coronary artery calcium,” Professor Adams said. 

“If we use the higher reading arm, we will diagnose more persons with hypertension or we will have more patients deemed not controlled, and that will alter the management of patients. 

“If we use the lower reading for systolic pressure, 30.2% of our participants would be at the 140mmHg threshold or above.”  

But if the higher reading was used, 38.5% would be at the 140mmHg threshold or above, he said. 

Professor Adams said a 1mmHg increase in systolic interarm pressure difference was associated with a 1% rise in 10-year all-cause mortality risk.