Performance of Simplified Scoring Systems for Hand Diagrams in Carpal Tunnel Syndrome Screening

Abstract

Katz et al have published a standardized scoring system of hand diagrams for carpal tunnel syndrome. The purpose of this study was to quantitatively evaluate an alternative scoring of the hand diagram for detection of carpal tunnel syndrome. In a prospective study of 1,107 workers, 221 workers with hand symptoms completed hand diagrams and electrodiagnostic testing for carpal tunnel syndrome. Scoring algorithms for the hand diagrams included the Katz rating; a median nerve digit score (0-2) with a maximum of 2 symptomatic digits of thumb, index, and long fingers; and isolated digit scores (0-1) of thumb, index, or long finger. Intraclass correlation coefficients quantified inter-rater reliability. Sensitivity, specificity, and logistic regression analyses evaluated the scoring systems' ability to predict abnormal median nerve conduction. One hundred ten subjects illustrated symptoms within the median nerve distribution. All scoring systems demonstrated substantial inter-rater reliability. "Classic" or "probable" Katz scores, median nerve digit score of 2, and positive long finger scores were significantly associated with abnormal median nerve distal sensory latency and median-ulnar difference. Abnormal distal motor latency was significantly associated with the median nerve digit score of 2 and positive long finger scores. Increasing Katz scores from "possible" to "probable" and "classic" were not associated with greater odds of electrodiagnostic abnormality. Positive long finger scores performed at least as well as the most rigorous scoring by Katz. Symptoms diagrammed within the median nerve distribution are associated with abnormal nerve conduction among workers. The median nerve digit score and the long finger score offer increased ease of use compared to the Katz method, while maintaining similar performance characteristics. The long finger appears best suited for isolated digit scoring to predict abnormal median nerve conduction in a working population. Diagnostic II.