Neuropad: evaluation of three cut-off points of sudomotor dysfunction for early detection of polyneuropathy in recently diagnosed diabetes

Abstract

Aims: To examine the sensitivity and specificity of three cut-off points of Neuropad for the diagnosis of distal symmetric polyneuropathy and small-fibre dysfunction in patients within the first year after diagnosis of diabetes.

Methods: Neuropad results were read at 10, 15 and 20 min and evaluated for diagnostic utility in distal symmetric polyneuropathy confirmed by electrophysiology and small-fibre dysfunction in 52 patients with Type 1 diabetes and 99 patients with Type 2 diabetes.

Results: The prevalence of distal symmetric polyneuropathy was 15.4% in Type 1 diabetes and 43.4% in Type 2 diabetes, while that of small-fibre dysfunction was 9.6 and 31.3%, respectively. Sensitivity of Neuropad for the diagnosis of distal symmetric polyneuropathy and small-fibre dysfunction was highest in Type 1 diabetes for the 10-min threshold reaching 87.5 and 80.0%, respectively, while it was modestly high in Type 2 diabetes at 65.1 and 67.7%, respectively. Specificity in both diabetes types was modest for the 10-min threshold (44.7-48.2%). It was highest for the 20-min threshold (83.8-89.3%) at the cost of poor sensitivity at 12.5-34.9%. Negative predictive values were relatively high for all three cut-off points in both types of diabetes (64.1-97.1%) at the cost of poor positive predictive values at 12.5-71.4%.

Conclusions: In patients within the first year after diagnosis of diabetes, the 10-min cut-off for Neuropad provides a relatively high sensitivity and modest specificity for distal symmetric polyneuropathy and small-fibre dysfunction, rendering the test more suitable as a screening tool than the 15- and 20-min cut-offs.