Comparison of different blood pressure indices for the prediction of prevalent diabetic nephropathy in a sub-Saharan African population with type 2 diabetes

BACKGROUND The association between blood pressure (BP) and diabetic kidney diseases in Africans has been less well investigated. We assessed and compared the strength of the association and discriminatory capability of systolic (SBP), diastolic (DBP) BP, pulse pressure (PP) and mean arterial blood pressure (MAP) for nephropathy risk in sub-Saharan Africans with type 2 diabetes. METHODS Participants were 420 consecutive individuals (49% men) with type 2 diabetes receiving chronic care in two main referral centres in the two major cities of Cameroon. Logistic regression models were used to compute the odd ratio (OR) and 95% confidence interval (95% CI) for a standard deviation (SD) higher level of SBP (25 mmHg), DBP (13), PP (18) and MAP (16) with nephropathy risk. Discrimination was assessed and compared with c-statistics and relative integrated discrimination improvement (RIDI, %). RESULTS The adjusted OR (95% CI) for nephropathy with each SD higher BP variable were: 1.45 (1.15-1.84) for SBP, 1.33 (1.06-1.66) for DBP, 1.35 (1.06-1.71) for PP and 1.42 (1.13-1.78) for MAP. C-statistic comparison showed no difference in discrimination of models with each of the BP variables (p-values ≥ 0.69 for c-statistics comparison). However, RIDI statistic always showed and enhancement in models discrimination when other BP variables were replaced with SBP, although such an enhancement was marginal for MAP. Using BP combination modestly improved models? discrimination. CONCLUSION SBP was the best predictor of prevalent nephropathy in this population, while DBP was the less effective. This may have implication for kidney disease risk stratification and protection.