Diagnostic capability of the scratch collapse test compared with other clinical diagnostic tests for diagnosis of carpal tunnel syndrome: a prospective case-control study

Abstract

Background: Diagnostic performance of the scratch collapse test for carpal tunnel syndrome (CTS) is not clear. This study evaluated its diagnostic capability for CTS diagnosis in comparison with other widely used clinical CTS tests, including the Tinel’s sign, Phalen’s test, and Durkan’s test. Methods: In a prospective case-control study, 78 CTS patients and 78 group-matched healthy control subjects were included. The electrodiagnostic testing was regarded as a reference standard CTS diagnostic method. The tests were conducted separately for the case and control groups; the sensitivity, specificity, positive predictive value (PPV), negative predictive value (NPV), and accuracy of the tests were calculated. Results: The sensitivity, specificity, PPV, NPV, and accuracy of CTS diagnosis were 7.7%, 100%, 100%, 52% and 53.8% for the scratch collapse test; 91%, 97.4%, 97.3%, 91.6%, and 94.2% for the Tinel’s sign test; 84.6%, 100%,100%, 88.6%, and 93.6% for the Phalen’s test; and 87.2%, 100%, 100%, 88.6%, and 93.6% for the Durkan’s test, respectively. Conclusions: Scratch collapse test has a low sensitivity and accuracy for diagnosing CTS. These results do not support its routine use for the diagnosis of CTS. Level of Evidence: Level III