Scratch Collapse Test for Carpal Tunnel Syndrome: A Systematic Review and Meta-analysis

Background: Despite the fact that carpal tunnel syndrome (CTS) is the most common entrapment neuropathy, the diagnostic accuracy of clinical screening examinations for CTS is controversial. The scratch collapse test (SCT) is a novel test that may be of diagnostic advantage. The purpose of our study was to determine the diagnostic accuracy of the SCT for CTS. Methods: A literature search was performed using PubMed (1966 to April 2018); Ovid MEDLINE (1966 to April 2018); EMBASE (1988 to April 2018); and Cochrane Central Register of Controlled Trials (The Cochrane Library, to April 2018). We examined the studies for the pooled sensitivity, specificity, and likelihood ratios of the SCT. This review has been registered with PROSPERO (CRD42018077115). Results: The literature search generated 13 unique articles. Seven articles were included for full text screening and 3 articles met our inclusion criteria, all of which were level II evidence with low risk of bias (165 patients). Pooled sensitivities, specificities, positive likelihood ratio, and negative likelihood ratios were 0.32 [95% CI (0.24-0.41)], 0.62 [95% CI (0.45-0.78)], 0.75 [95% CI (0.33-1.67)], and 1.03 [95% CI (0.61-1.74)], respectively. The calculated area under the summary receiver operating characteristic (AUSROC) curve was 0.25, indicating a low diagnostic accuracy. Conclusion: The SCT has poor sensitivity; however, it is moderately specific. Based on the current literature and their variable quality of the evidence, we conclude that the SCT is not an adequate screening test for detecting CTS.