RESUMO
Ambulatory blood pressure monitoring (ABPM) is an accurate method for evaluating hypertension, yet its use in clinical practice may be limited by availability, cost and patient inconvenience. The objective of this study was to investigate the ability of a 6-h ABPM window to predict blood pressure control, judging by that of the full 24-h ABPM session across several clinical indications in a cohort of 486 patients referred for ABPM. Sensitivities and specificities of the 6-h systolic blood pressure mean to accurately classify patients as hypertensive were determined using a fixed reference point of 130 mm Hg for the 24-h mean. For four common indications, in which ABPM was ordered, prediction tables were constructed varying the thresholds for the 6-h mean to find the optimal value that best predicted the 24-h hypertensive status as determined from the full 24-h interval. Using a threshold of 137 mm Hg for the indications of borderline hypertension, evaluation of current antihypertensive regimen and suspected white-coat hypertension, sensitivity and specificity ranged from 0.83-0.88 to 0.80-0.88, respectively, for the ability of 6-h ABPM to correctly categorize hypertensive status. Using 133 mm Hg as the threshold for treatment resistance resulted in a sensitivity and specificity of 0.93 and 0.83, respectively. We conclude that a shortened ABPM session of 6 h can be used to accurately classify blood pressure as controlled or not, based on the results of a 24-h session. The optimal 6-h threshold for comparison depends upon indication for referral.
