Reliability and diagnostic validity of clinical examination and patient self-report measures in carpal tunnel syndrome

Abstract

Study Design: A blinded, prospective diagnostic test study was conducted.Objectives: To assess the inter-tester reliability of clinical examination items for carpal tunnel syndrome (CTS), to assess the validity of individual clinical test items and self-report measures for the diagnosis of CTS and to assess the accuracy of an optimum test item cluster for the diagnosis of CTS.Study Rational: Examination of the diagnostic validity of various clinical tests for the diagnosis of CTS has shown mixed results and the reliability of many of these tests has not been determined. The majority of the diagnostic validity research for CTS has examined tests individually which is in contrast to clinical practice where the results of multiple tests are combined as part of the clinical reasoning process in order to formulate a differential diagnosis: the test item cluster, derived through logistic regression, is proposed as a means to integrate the validity of multiple tests. Methods: 37 subjects (74 “hands”) were recruited from a convenience sample of consecutive patients referred to for electrodiagnostic (EDX) testing due to upper extremity symptomatic complaints. Subjects underwent EDX testing followed by completion of self-report questionnaires and a standardized clinical examination by examiners blinded to EDX results. Diagnostic validity was determined for both “general” and “restricted” CTS classification groupings. Results: Out of 18 clinical test items, 12 had reliability coefficients (i.e. ICC or Kappa) of .40 or greater. There were 10 clinical exam and self-report items that were found to have likelihood point estimates above 2 or below 0.50 for the general diagnostic classification and 6 items had acceptable validity for the restricted classification. The test item cluster (TIC) derived for the general classification included “hand numbness” and symptom reproduction with the upper limb neurodynamic test 1. The TIC derived for the restricted classification included “hand numbness” and the overall score of the symptom component of the Bringham Carpal Tunnel Questionnaire. The 95% confidence intervals for most likelihood ratio point estimates were wide. Conclusions: The TICs for both classification groupings did not yield improved diagnostic validity beyond that found with the single best test item (“hand numbness”). The value of the single best test item “hand numbness” was in a negative response. Further investigation is required to validate the TIC and the single best test item and to improve the point estimate precision.