Purpose: The purpose of this study was to evaluate the clinical usefulness of a new test, the scratch collapse test, for the diagnosis of carpal tunnel syndrome and cubital tunnel syndrome.
Methods: The scratch collapse test was prospectively compared with Tinel's sign and flexion/nerve compression in 169 patients and 109 controls. One hundred nineteen patients were diagnosed with carpal tunnel syndrome and 70 patients were diagnosed with cubital tunnel syndrome based on history, examination, and positive electrodiagnostic test. For the new test, the patient resisted bilateral shoulder external rotation with elbows flexed. The area of suspected nerve compression was lightly "scratched," and then resisted shoulder external rotation was immediately repeated. Momentary loss of shoulder external rotation resistance on the affected side was considered a positive test. The sensitivity, specificity, and predictive values were calculated.
Results: For carpal tunnel syndrome, sensitivities were 64%, 32%, and 44% for the scratch collapse test, Tinel's test, and wrist flexion/compression test, respectively. For cubital tunnel syndrome, sensitivities were 69%, 54%, and 46% for the scratch collapse test, Tinel test, and elbow flexion/compression test, respectively. The scratch collapse test had the highest negative predictive value (73%) for carpal tunnel syndrome. Tinel's test had the highest negative predictive value (98%) for cubital tunnel syndrome. Specificity and positive predictive values were high for all of the tests.
Conclusions: The scratch collapse test had significantly higher sensitivity than Tinel's test and the flexion/nerve compression test for carpal tunnel and cubital tunnel syndromes. Accuracy for this test was 82% for carpal tunnel syndrome and 89% for cubital tunnel syndrome. This novel test provides a useful addition to existing clinical maneuvers in the diagnosis of these common nerve compression syndromes.
Type of study/level of evidence: Diagnostic II.