The Scratch-Collapse Test: A Systematic Review and Statistical Analysis.

backgroundThe scratch-collapse test (SCT) is a provocative maneuver used to diagnose compressive neuropathies. Despite multiple studies supporting its use, the SCT remains a controversial point in the literature in regard to its exact clinical application. We performed a systematic review and statistical analysis to provide statistical data on SCT outcomes and elucidate its role in diagnosing compressive conditions.

methodsWe performed a systematic review of the literature according to Preferred Reporting for Systematic Reviews and Meta-Analyses guidelines. We extracted data of patients with outcomes on the SCT (yes/no) and on an accepted gold standard examination (electrodiagnostic studies). These data were analyzed using a statistical software program to generate the sensitivity and specificity values of the pooled data, as well as kappa agreement statistics.

resultsFor patients with carpal tunnel, cubital tunnel, peroneal, and pronator compressive neuropathies, the overall sensitivity of the SCT was 38%, and the specificity was 94%, with the kappa statistic approximately 0.4. Sensitivity and specificity values were higher for cubital tunnel syndrome and peroneal compression syndrome but lower for carpal tunnel syndrome. Pronator syndrome was also examined, but the data were inadequate for analysis.

conclusionsThe SCT is a useful adjunct in the armament of diagnostic tools for the hand surgeon. Given its low sensitivity and high specificity, SCT should be used as a confirmatory test, rather than as a diagnostic screening test. More analyses are needed to identify subtler applications.