Validity of clinic blood pressure compared to ambulatory monitoring in hypertensive patients in a primary care setting

Aims. To determine the validity of the blood pressure (BP) measurement in a primary care setting in comparison with the measurement obtained from 24-h ambulatory blood pressure monitoring (ABPM). Methods. Patients with hypertension (n = 137) were studied in primary care. Immediately after a nurse took two measurements of each patient's BP, the ABPM device was attached. Agreement was determined using the Bland-Altman method and the Kappa index. The sensitivity, specificity, predictive values and likelihood ratios were calculated for the manual BP measurement in comparison with ABPM for the purpose of diagnosing uncontrolled BP. Results. The BP values from ABPM were lower than those obtained in the examination room. The difference between the clinic measurement and the ABPM was 18.07 +/- 14.6 mmHg (systolic blood pressure, SBP) and 6.3 +/- 9.2 mmHg (diastolic blood pressure, DBP). The agreement between the clinic measurement and 24h-ABPM for the purpose of classifying control or uncontrolled RP was 64.2% (Kappa=0.311). In the case of ABPM, the sensitivity of the measurement in the examination room for diagnosing uncontrolled BP was 80.36%, specificity was 53.09%, positive predictive value 54.22% and negative predictive value 70.63%. Conclusions. Clinic measurements do not have sufficient sensitivity/specificity to be recommended as a single method of BP control in primary care.