The research by Dr Christopher Clark, of the Mid Devon Medical Practice in Witheridge, is the first systematic review of risk factors associated with BP differences between arms.
Inter-arm differences in BP are common among people at risk of cardiovascular disease. Previous work has suggested the differences could be used as a predictor of developing these diseases and of mortality.
NICE guidelines call for BP checks on both arms and warn that if the difference is more than 20mmHg, future checks should be on the arm with the higher reading. But researchers said many clinicians fail to follow this advice.
Dr Clark's team at the University of Exeter examined 230 patients at his practice from 1999 to 2002. They found 24% had average differences in inter-arm systolic BP of 10mmHg or more, while 9% had a difference of 15mmHg or more.
During the study, 44% of patients developed vascular disease or died. They were at 9% greater risk of a cardiovascular event for every 1mmHg greater difference between BP readings.
Dr Clark said: 'This study supports the potential value of an inter-arm difference as a simple indicator of increased cardiovascular risk.'
He said this assessment should be a 'core component' of primary care BP measurement and that inter-arm differences should prompt consideration of further assessment and aggressive management of risk factors.
But in an accompanying editorial, Dr Dae Hyun Kim of Harvard Medical School said the study may have misclassified patients with highly variable BP. This and other limitations mean it 'cannot be considered definitive', he said.