The accuracy of community-based automated blood pressure machines

Despite widespread use, the accuracy of community-based automated blood pressure machines has been questioned. We sought to determine if these machines are as accurate and reliable as those obtained by a clinician with a mercury manometer.

We randomly selected 25 pharmacies and compared blood pressure readings obtained from their automated machines with from a mercury manometer. We used 3 volunteers with arm circumferences at the low, medium, and high ends of the acceptable range of a normal adult cuff size.

For the subject with the small arm size, store machines reported systolic pressure readings that were, on average, 10 mm Hg higher than those obtained by the clinician (P <.001) and diastolic pressures 9 mm Hg higher (P <.001). The mean systolic pressure readings for the subject with the medium arm size were not significantly different between the store machine and the mercury manometer, and the readings were only modestly different for diastolic pressure. For the subject with the large arm size, store machines reported diastolic pressure readings that were, on average, 8.3 mm Hg lower than those obtained using the mercury manometer (P <.001), but with no significant difference in the systolic pressure.

We found that automated blood pressure machines from a representative community-based sample of pharmacies did not meet the accepted standards of accuracy and reliability. Accuracy of readings is especially uncertain for patients having arm sizes larger or smaller than average.