A Prospective Comparison of Diagnostic Tools for the Diagnosis of Carpal Tunnel Syndrome

Abstract

Purpose: Nerve conduction studies (NCS), CTS-6, Wainner, Kamath, and Lo are diagnostic tests that are used to diagnose carpal tunnel syndrome (CTS). To our knowledge, no study has compared the sensitivity and specificity of these 5 tests with one another. The purpose of this study is to compare NCS, CTS-6, Wainner, Kamath, and Lo using clinical diagnosis by a hand fellowship-trained orthopedic surgeon as reference standard.

Methods: A hand fellowship-trained surgeon completed the CTS-6, Wainner, Kamath, and Lo diagnostic tools. Cutoff values for a positive test were based on values in the literature, if available. The NCS were performed by a certified electrodiagnostic physician according the standards of the American Association of Neuromuscular and Electrodiagnostic Medicine and were interpreted using absolute latencies, relative latencies, and combined sensory index. Sensitivity, specificity, positive predictive value, negative predictive value, positive likelihood ratio, and negative likelihood ratio were calculated for the tests using clinical diagnosis as the reference standard.

Results: A total of 408 wrists from 250 patients were analyzed in the study. The NCS had the highest sensitivity (94%) but also the lowest specificity (50%) of any of the diagnostic tests. Using a cutoff of 18, CTS-6 had the highest specificity (99%). The NCS had the highest area under the curve at 74%, followed closely by the Kamath at 69%.

Conclusions: The NCS were traditionally felt to be a strong confirmatory test given their high specificity. However, this prospective series demonstrated that NCS had the lowest specificity of any diagnostic test.

Clinical relevance: Consideration should be given to using alternative diagnostic tests/tools based on the results of this study.

Keywords: CTS-6; Carpal tunnel syndrome; Kamath; Lo; Wainner.