An assessment of discriminatory power of office blood pressure measurements in predicting optimal ambulatory blood pressure control in people with type 2 diabetes

Abstract

Introduction: ambulatory blood pressure (BP) measurements (ABPM) predict health outcomes better than office BP, and are recommended for assessing BP control, particularly in high-risk patients. We assessed the performance of office BP in predicting optimal ambulatory BP control in sub-Saharan Africans with type 2 diabetes (T2DM).

Methods: participants were a random sample of 51 T2DM patients (25 men) drug-treated for  hypertension, receiving care in a referral diabetes clinic in Yaounde, Cameroon. A quality control group  included 46 non-diabetic individuals with hypertension. Targets for BP control were systolic (and diastolic) BP.

Results: mean age of diabetic participants was 60 years (standard deviation: 10) and median duration of diabetes was 6 years (min-max: 0-29). Correlation coefficients between each office-based variable and the 24-h ABPM equivalent (diabetic vs. non-diabetic participants) were 0.571 and 0.601 for systolic  (SBP), 0.520 and 0.539 for diastolic (DBP), 0.631 and 0.549 for pulse pressure (PP), and 0.522 and 0.583  for mean arterial pressure (MAP). The c-statistic for the prediction of optimal  ambulatory control from  office-BP in diabetic participants was 0.717 for SBP, 0.494 for DBP, 0.712 for PP, 0.582 for MAP, and 0.721 for either SBP+DBP or PP+MAP. Equivalents in diabetes-free participants were 0.805, 0.763, 0.695, 0.801 and 0.813.

Conclusion: office DBP was ineffective in discriminating optimal ambulatory BP control in diabetic  patients, and did not improve predictions based on office SBP alone. Targeting ABPM to those T2DM  patients who are already at optimal office-based SBP would likely be more cost effective in this setting.

Key words: Ambulatory blood pressure, office blood pressure, diabetes mellitus, prediction, sub-Saharan Africa, Cameroon