Accuracy of the Scratch Collapse Test for Carpal Tunnel Syndrome in Comparison With Electrodiagnostic Studies

Abstract

Background: The scratch collapse test (SCT) is a clinical examination maneuver that has been previously reported as a reliable and reproducible test to diagnose carpal tunnel syndrome (CTS). The initial study by Cheng et al in 2008 showed a simple test with high sensitivity. However, subsequent attempts to reproduce those findings have resulted in lower accuracy. Our goal was to evaluate the use of the SCT for patients presenting with symptoms of pain, numbness, or weakness in an upper extremity. Methods: Forty patients were referred to the electrodiagnostic (EDX) lab for evaluation of an upper extremity. One blinded examiner who was familiar with the maneuver performed the SCT on all 40 patients. Another physician or technician performed the nerve conduction study and electromyography. Patient history and accompanying physical examination findings were not revealed to the SCT examiner. Results: The relationship between the SCT performed by a blinded examiner and the EDX performed by blinded examiners was nonsignificant ( P = .676) and showed a sensitivity of 0.48, specificity of 0.59, positive predictive value of 0.61, and negative predictive value of 0.45. Conclusion: Based on this study and previous findings by other authors, we would advise against the use of the SCT in CTS for important patient-care decisions, such as surgical decision-making, until future research is done. It is possible that the SCT, in combination with other physical examination maneuvers, could increase diagnostic accuracy and enhance patient management.

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

“…The poor diagnostic capability of the scratch collapse test in the CTS diagnosis has also been demonstrated in other studies 6,15,16. Altogether, the results of the present study, adjunct with the results of earlier investigations, advise against the implication of the scratch collapse test in CTS diagnosis.…”

Reply: Practice Patterns and Testing for Carpal Tunnel Syndrome

“…To echo previous commentary on this approach, 3 objective measurements, including craniometric angle measurements, intracranial volumes, and more recently, artificial intelligence, are available when assessing metopic synostosis. 4,5 In response, the authors have previously cited a study by Anolik et al to argue that interfrontal angle measurement correlates with expert assessment. 6 However, expert assessment in that study was based on computed tomographic imaging rather than external visual assessment.…”

“…due to their low reliability. [2][3][4] The comment we cited by Hermiz and Kalliainen, 5 indicating that electrodiagnostic studies add little to the diagnosis of carpal tunnel syndrome, was published as part of the American Board of Plastic Surgeons' evidence-based medicine series in 2017. Dr. Walker has provided sufficient evidence that this comment should be updated, and we agree that formal imaging can augment the diagnosis of carpal tunnel syndrome in cases where clinical judgment alone is insufficient to draw meaningful conclusions.…”

“…1 Dr. Walker has highlighted in his commentary several recent studies showing a high level of evidence in support of ultrasound utilization in carpal tunnel syndrome diagnosis and against the widespread use of certain physical examination maneuvers such as the scratch collapse test, due to their low reliability. 2–4 The comment we cited by Hermiz and Kalliainen, 5 indicating that electrodiagnostic studies add little to the diagnosis of carpal tunnel syndrome, was published as part of the American Board of Plastic Surgeons’ evidence-based medicine series in 2017. Dr. Walker has provided sufficient evidence that this comment should be updated, and we agree that formal imaging can augment the diagnosis of carpal tunnel syndrome in cases where clinical judgment alone is insufficient to draw meaningful conclusions.…”

Practice patterns and testing for carpal tunnel syndrome.

“…2–4 Furthermore, while physical examination improvisations are desirable, recent articles on the “scratch collapse test” have failed to confirm its suitability as a technique for widespread application. 5 Unlike the scratch collapse test, monofilament testing, two-point discrimination, and other bedside tests, nerve conduction studies and ultrasound are well standardized and require neither active participation by patients nor introspective interpretation of applied stimuli. This may explain why hundreds of different laboratories have confirmed the value of ultrasound and electrodiagnosis in carpal tunnel syndrome while only a handful of studies have attempted to validate subjective measures that are resistant to formal quantification.…”