It has been recommended to take the average of several blood pressure (BP) determinations with a sphygmomanometer to diagnose hypertension, but there is no agreement on the reading numbers. PURPOSE. Describing the behavior of BP readings taken in three different days to establish the classificatory BP in an outpatient hypertension clinic. METHOD. In the outpatient hypertension clinic of the Clinical Pharmacology Division of the Hospital de Clínicas de Porto Alegre, we use the mean of six readings taken in three different days to establish the classificatory blood pressure, except for those with very high or low values in the first day. In this report we describe the behavior of BP in 58 patients submitted to this routine. RESULTS. The mean of systolic (SBP) and diastolic (DBP) blood pressures decreased from the first to the 6th reading (ANOVA for repeated measurements: F = 4.45, P = 0.001 for SBP and F = 5.54, P < 0.001 for DBP). Afterward, the patients were classified into two groups according their first SBP and DBP reading. The decreasing in both SBP and DBP was confined to those with the first measurement in the upper half of the entire group (ANOVA: F = 8.03; P < 0.0001 for SBP and F = 6.33, P <0.0001 for DBP). Regression to the mean and some reactiveness in the first day are possible explanations for this. CONCLUSION. These data corroborate that the hypertension diagnosis should not be based in an single blood pressure determination and suggest that the recommendation to diagnose severe hypertension based on high values in the first two read-ings could misclassify some patients.
Hypertension; Blood pressure; Several readings