Evaluation of the Vita-Stat automatic blood pressure recorder. A comparison with the Random-Zero sphygmomanometer.

A total of 408 adult volunteers at Northwick Park Hospital, England, participated in an evaluation of the Vita-Stat automatic blood pressure (BP) recorder. During a five-day period in March 1981, readings of BP obtained by two Vita-Stat machines were compared with measurements obtained by two trained observers using Random-Zero sphygmomanometers. The order in which BP readers were obtained was randomized. A significant effect of order on systolic BP was removed from comparisons between techniques. For diastolic BP values, there was close agreement between the different measurement techniques and each was associated with a similar degree of repeatability between duplicate recordings. In contrast, both Vita-Stat machines seriously overestimated systolic BP and there was substantially more variability between duplicate readings of systolic BP obtained with the Vita-Stat machines than for Random-Zero values. The use of either Vita-Stat machine for population screening would have correctly identified almost all those with a high BP but would have led to considerable overdiagnosis of systolic hypertension. Despite their limitations, the accuracy of diastolic BP estimates and considerations of cost and convenience suggest that Vita-Stat machines might be useful as initial screening tools for detection of persons with high diastolic BP. However, the use of a particular Vita-Stat machine should be preceded by an evaluation of the machine against a standard method of BP estimation.