Department of Community Health Sciences, UCLA School of Public Health, Los Angeles, CA 90095-1772, USA

Correspondence to: Donald E Morisky, UCLA School of Public Health, Box 951772 Los Angeles, CA 90095-1772, USA

The purpose of this study is to assess the relative stability of the systolic and diastolic blood pressure (BP) measures obtained in a state-wide screening programme. A state-wide hypertension survey was conducted in California in 1983 in which a total of 6381 adults were interviewed in their homes. Three BP measurements were taken, with a 5-min interval between each measure. The BP screening protocol used by The Joint National Committee on Detection, Evaluation and Treatment of High Blood Pressure recommended a total of three measures, in which the second and the third measures are averaged. Results of the household survey indicated significant differences between the three subsequent BP measurements (P < 0.001), with much smaller differences between the second and third measure. this result implies that bp of an individual is approaching stability after the second measure and, consequently, two subsequent bp measurements may be sufficient to identify subjects with elevated bp. we compare the three-measure screening protocol with a two-measure screening protocol in which only the first two bp readings are taken and the second reading is used to indicate bp levels of subjects. the percentage of agreement between the three-measure and the two-measure screening protocols is 97.57%. using the three-measure screening protocol as a standard, the sensitivity and false-negative rate are 98.73% and 0.43%, respectively. the two-measurement screening protocol is recommended as an equally sensitive and a more efficient procedure for a large-scale community-screening programme.

blood pressure measurement; hypertension; sensitivity; specificity