Usefulness of ambulatory blood pressure monitoring in predicting the presence of autonomic neuropathy in type I diabetic patients.

This study investigated whether nondipping (defined as a day–night change in blood pressure (BP) <=0%) could be assumed as a diagnostic index for autonomic neuropathy, and assessed its accuracy in discriminating between type I diabetic patients with and without autonomic neuropathy. In 87 type I diabetic patients with normal renal function (age 36+-11, duration 17+-9 years, serum creatinine 67.2+-15.9 mcmol/l), four cardiovascular tests and 24-h BP monitoring were performed, and the percentage day–night change (Delta) in systolic (SBP) and diastolic BP (DBP) was calculated. Sixteen patients had Delta SBP and/or Delta DBP <=0%. In a multiple logistic regression with adjustment for sex, age, and body mass index, the odds ratio for having autonomic neuropathy was seven times higher in patients with DSBP <=0% as opposed to those without (odds ratio 6.97, CI 1.4–34.9, P=0.018). Using Receiver Operating Characteristic (ROC) analysis, DBP showed an acceptable accuracy in discriminating between patients with and without autonomic neuropathy (area under the ROC curve 0.69+-0.06 and 0.72+-0.05 for Delta SBP and Delta DBP, respectively). Adequate cutoff values were 0% for Delta SBP (sensitivity, 26%; specificity, 95%; positive predictive value, 87%) and 5% for Delta DBP (sensitivity, 26%; specificity, 92%; positive predictive value, 81%). In type I diabetic patients with normal renal function, a value of Delta SBP p0% identifies the presence of autonomic neuropathy with a very high chance. Nondipping at the cutoff proposed could be considered an adjunctive marker of autonomic neuropathy provided with a high specificity and low sensitivity.