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

Updates to the Physiologic Mechanism, Anatomical Sites, and Diagnostic Utility of the Scratch Collapse Test: A Systematic Review

Background

The scratch collapse test (SCT) has gained popularity as a physical examination technique for diagnosing compression neuropathy. This systematic review aims to assess the reliability of the SCT as a diagnostic tool for compression neuropathy, as well as to propose the underlying physiological mechanisms involved. Specific criteria was developed to broaden the potential anatomical applications of the SCT.

Methods

A literature search was conducted using PubMed, Embase, Scopus, and Google Scholar. Eleven articles meeting predefined inclusion/exclusion criteria were selected for numerical analysis, which yielded sensitivity, specificity, positive predictive value (PPV), negative predictive value (NPV), and accuracy values.

Results

In total, 890 patients with carpal tunnel syndrome were reported in 10 studies. The mean (±SD) sensitivity, specificity, PPV, NPV, and accuracy were 0.442 ± 0.272, 0.788 ± 0.163, 0.834 ± 0.143, 0.433 ± 0.297, and 48.8% (range, 31%-82%), respectively. Of the studies that provided interrater reliability (κ), the mean was 0.544 ± 0.441, indicating moderate agreement. A total of 121 patients with cubital tunnel syndrome were reported in three studies, with a mean (±SD) sensitivity and specificity of 0.635 ± 0.367 and 0.945 ± 0.06, respectively. Twenty-four patients with peroneal nerve compression, reported in one study, had sensitivity, specificity, PPV, NPV, and accuracy of 0.77, 0.99, 0.95, 0.92, and 93%, respectively.

Conclusions

Current literature indicates that the SCT can serve as a provocative test to assist in diagnosing compression neuropathy. Nevertheless, the heterogeneity of reported values underscores the necessity for further investigation aimed at enhancing the objectivity of SCT, thus improving interrater reliability and minimizing potential bias.

Sensitivity and Specificity of Examination Maneuvers for Carpal Tunnel Syndrome: A Meta-Analysis

Our purpose was to assess the diagnostic validity (sensitivity (Sn) and specificity (Sp)) of physical examination maneuvers for carpal tunnel syndrome (CTS). This meta-analysis utilized the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) checklist. Studies assessing exam maneuvers (including components of the CTS-6) for CTS were identified in MEDLINE (Medical Literature Analysis and Retrieval System Online) and Embase (Excerpta Medica Database) databases. Assessed maneuvers assessed included: Phalen's test, Tinel's sign, Durkan test, scratch-collapse test, Semmes-Weinstein monofilament (SWM), and static 2-point discrimination (2PD) test. Data extracted included: article name, total number of subjects/hands, type of exam, and exam Sn/Sp. Forest plots were presented to display the estimated Sn/Sp and boxplots were used to demonstrate the locality, spread, and skewness of the Sn/Sp through the quartiles. After screening 570 articles, 67 articles involving 8924 hands were included. Forty-eight articles assessed Phalen's test, 45 assessed Tinel's sign, 21 assessed the Durkan test, seven assessed the scratch-collapse test, 11 assessed SWM, and six assessed the static 2PD test. Phalen's test demonstrated the greatest median Sn (0.70, (Q1, Q3): (0.51, 0.85)), followed by the Durkan test (0.67, (Q1, Q3): (0.46, 0.82)). 2PD demonstrated the highest median Sp (0.90, (Q1, Q3): (0.88, 0.90)), followed by SWM (0.85, (Q1, Q3): (0.51, 0.89)). There is considerable variability with respect to the validity of physical exam tests used in the diagnosis of CTS. Upper-extremity surgeons should be aware of inherent limitations for individual exam maneuvers. In the absence of a uniformly accepted diagnostic gold standard, a combination of exams, along with pertinent patient history, should guide the diagnosis of CTS.