Negative and positive predictive value of preoperative clinical tests for autonomic neuropathy in diabetic surgical patients

The objective of this prospective observational study was to look at the sensitivity, specificity, overall accuracy, and positive and negative predictive value of some common clinical tests used to assess the autonomic dysfunction preoperatively. Thirty consecutive diabetic patients of ASA 1 to 3 status were compared to 30 non-diabetic age matched controls. A battery of tests was performed the day before surgery to assess sympathetic and parasympathetic function. These tests included detecting symptoms of neuropathy on clinical history, resting heart rate, heart rate variation during deep breathing, blood pressure response to standing, and to sustained hand grip. Sensitivity, specificity, overall accuracy and positive and negative predictive values were calculated with standard formulas. Heart rate variation to deep breathing was calculated to have the highest sensitivity (93%) whereas blood pressure response to standing had the highest specificity (100%). The least sensitive test was the blood pressure response to standing (26%) and response to sustained hand grip (13%). Tests with high specificity will be important in anaesthesia as they will help to diagnose the presence of autonomic neuropathy in patients. These were blood pressure response to standing and presence of 2 symptoms on history. Tests with high sensitivity which can be used to rule out autonomic involvement were heart rate variation to deep breathing and blood pressure response to sustained hand grip.