OBJECTIVE: Given the controversial aspects of orthostatic hypotension (OH) testing in diabetes, we evaluated the diagnostic role for cardiac autonomic neuropathy (CAN) and for nondipping of OH, defined according to a fall in systolic blood pressure (BP) > or = 30 (30-OH) or > or = 20 mmHg (20-OH). METHODS: 164 diabetic patients underwent 24 hours BP monitoring, three heart rate cardiovascular tests, and OH test. RESULTS: Compared to 30 mmHg, the 20 mmHg criterion increased the frequency of OH from 11 to 19.5%. Both 30-OH and 20-OH were associated with CAN (chi(2)=30.5, P <0.0001, and chi(2)=45.1, P <0.0001, respectively) and nondipping (chi(2)=31.7, P <0.0001, and chi(2)=17.2, P=0.0001, respectively). ROC curve for orthostatic systolic BP fall provided an AUC of 0.79 +/- 0.04 (95% CI 0.70-0.86) for diagnosing CAN and of 0.77 +/- 0.05 (95% CI 0.66-0.86) for diagnosing nondipping. Both 30-OH and 20-OH showed a low sensitivity and high specificity for CAN [sensitivity 31%, specificity 98%, Likelihood Ratio for a positive result (LR(+)) 17.1; and sensitivity 50%, specificity 95%, LR(+) 9.3, respectively], and for nondipping (sensitivity 40%, specificity 96%, LR(+) 8.9, and sensitivity 47%, specificity 87%, LR(+) 3.5, respectively), having 30-OH a higher LR(+) in both cases. INTERPRETATION: OH had only moderate diagnostic accuracy, with high specificity and low sensitivity, for CAN, diagnosed on the basis of heart rate cardiovascular tests, and-as a novel finding-also for nondipping. A different definition of OH did not substantially affect its diagnostic characteristics, with just a slightly greater ability of the 30 mmHg criterion to estimate the probability of CAN and nondipping
