Background: Electrodiagnostic studies are commonly used to diagnose carpal tunnel syndrome. However, these examinations are prone to false-positive and false-negative values. The authors evaluated the agreement of electrodiagnostic study severity, clinical assessment scores, and probability of carpal tunnel syndrome [Six-Item Carpal Tunnel Syndrome Evaluation Tool (CTS-6) scores.
Methods: This was a retrospective cohort study of 609 patients with carpal tunnel syndrome (941 hands). Data were collected from nine hand surgery practices in the Michigan Collaborative Hand Initiative for Quality in Surgery. Goodman and Kruskal gamma statistics (γ) measured the agreement between electrodiagnostic studies and clinical assessment scores and between electrodiagnostic studies and CTS-6 scores. The authors performed cumulative logistic regression with mixed effects to evaluate the association among electrodiagnostic study severity, clinical assessments, and patient characteristics.
Results: The concordance between electrodiagnostic study severity and CTS-6 scores was γ = 0.31 (95 percent CI, 0.21 to 0.40), with an accuracy of 43 percent. The concordance between electrodiagnostic study severity and clinical assessment scores was γ = 0.66 (95 percent CI, 0.58 to 0.74), with an accuracy of 58 percent. Wide site-level variation in the γ coefficient between electrodiagnostic studies and clinical assessment scores and between electrodiagnostic studies and CTS-6 was seen. Male sex, increasing age, and increasing body mass index were significantly associated with increased odds of electrodiagnostic study severity.
Conclusions: Wide practice-level variation underscores the variability in diagnostic testing accuracy. Physicians should consider patient characteristics (e.g., sex, age, body mass index) when assessing carpal tunnel syndrome severity.
Clinical question/level of evidence: Diagnostic, II.
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