Objective Evaluation of the "Scratch Collapse Test" for the Diagnosis of Cubital Tunnel Syndrome Using Dynamometer

This study aimed to objectively evaluate the sensitivity and specificity of the scratch collapse test (SCT) for the diagnosis of cubital tunnel syndrome (CuTS). We conducted a comparative experimental study to measure the force of shoulder external rotation using a dynamometer instead of the subjective outcome reported by examiners.

The force of shoulder external rotation was measured using a dynamometer while performing a SCT. Sixteen patients with electrodiagnostically confirmed CuTS and 20 healthy volunteers were included in this study. The difference between the external rotation force before and after the SCT was calculated in Newtons and expressed as a percentage change. A negative value indicated a reduction in force after the scratch maneuver. The sensitivity, specificity, accuracy, positive predictive value, and negative predictive value were calculated from the test results of the patient and control groups.

The sensitivity of the SCT was 37%, whereas the specificity was 75%. The positive predictive value was 0.55, and the negative predictive value was 0.60. The overall accuracy of the SCT was 58%.

The SCT has been described initially as an accurate and useful diagnostic test for CuTS. Our result using a more objective method of measurement demonstrated relatively lower accuracy compared with previous studies.

Diagnostic II.