Blood pressure reclassification in adolescents based on repeat clinic blood pressure measurements

The common assumption is that blood pressure (BP) will decrease on subsequent readings. The objective of this study is to examine the prevalence and direction of BP classification change with repeat measurements and compare common clinical characteristics of groups of patients who do and do not have a change in BP classification. A nationally representative subsample of 1725 adolescents aged 13 to 18 years from the National Health and Nutrition Survey were analyzed. Three BP measurements were obtained. Patients were classified based on the first and the average of 3 BP measurements as having normal BP, hypertension, and/or prehypertension. Of the 1725 adolescents, 1569 (90.9%) maintained BP classification, 107 (6.2%) had a reduction in their classification, and 49 (2.9%) had an increase in their classification. Comparing the two groups that changed BP classification to the group without change, C-reactive protein and body mass index (BMI) z score were significantly higher in the groups that had a change in BP classification (P=.02 and <.001, respectively). After adjusting for other variables, higher BMI value was significantly associated with change in BP classification. With repeat measurements, the majority (~91%) did not have a change in classification. Obesity was a significant predictor of the 9% that had a change in classification. Repeat BP measurements in obese adolescents may lead to more accurate classification of BP status.