Development and validation of a clinical model for predicting the severity of carpal tunnel syndrome

Abstract

ABSTRACT Objectives To develop a clinical instrument to assess carpal tunnel syndrome (CTS) severity before electrodiagnostic testing. Methods Data from 1037 patients with CTS (39.1% male) were included. The mean (SD) age was 58.0 (10.8) years. The severity of CTS was based on electrodiagnostic findings. Results We devised a composite index incorporating a pain numeric rating scale (NRS) rated from 0 (no pain at all) to 10 (the worst pain ever possible), thenar muscle weakness or atrophy (TW), cross-sectional area (CSA) of the median nerve (mm2), and nocturnal pain (NP). The index was calculated as [scale(NRS)+scale(CSA)+NP+TW]/4, where NP and TW are binary features (0 or 1). The accuracy and area under the curve of the index were 0.85 and 0.71, respectively (Cohen’s Kappa = 0.51, McNemar’s test P = 0.249). The index increased pretest probabilities by 1.6, 1.8, and 3.3 times with positive likelihood ratios of 3.3, 2.5, and 13.5, and false-positive rates of 26.6, 17.6, and 4.8% for mild, moderate, and severe CTS, respectively. The index thresholds for mild, moderate, and severe CTS were <0.8, ≥0.8 to <1.1, and ≥1.1, respectively. Conclusion Using a composite index, patients with CTS can be categorized for the severity of the syndrome.