Scratch collapse test had low sensitivity for carpal, cubital tunnel syndromes
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Regardless of whether a clinical or electrodiagnostic reference standard was used, the scratch collapse test had high specificity but low sensitivity for carpal tunnel syndrome and cubital tunnel syndrome, according to published results.
A resident and nerve conduction technician each performed the scratch collapse test on 92 patients referred for electrodiagnostic studies for upper extremity symptoms thought to be related to an entrapment mononeuropathy. Gerald Wolff, MD, and colleagues calculated sensitivity and specificity for the scratch collapse test using both electrodiagnostic testing results and used a validated clinical tool as the reference standard. Researchers also calculated interrater reliability.
Results showed the scratch collapse test had a sensitivity of 7% and a specificity of 78% for carpal tunnel syndrome when using electrodiagnostic criteria as a reference standard. When clinical criteria were used as a reference standard, researchers found the scratch collapse test had a sensitivity of 15% and a specificity of 87% for carpal tunnel syndrome, and a sensitivity of 10% and a specificity of 90% for cubital tunnel syndrome. Between the resident and the technician, the first interrater reliability of the scratch collapse test was worse than expected based on chance alone at -0.025, according to results. Researchers noted the second interrater reliability between the resident and technician indicated fair strength of agreement at 0.211.
“Our blinded study found the scratch collapse test had a very poor sensitivity for detecting carpal tunnel syndrome and cubital tunnel syndrome. In addition, there was poor interrater reliability,” Wolff told Healio Orthopedics. “Our study compliments the blinded study performed by Jeremy Simon, MD, and colleagues in 2017 and suggests that over reliance on the physical examination maneuver could lead to incorrect diagnoses when assessing patients for suspected carpal or cubital tunnel syndrome. This could lead to unnecessary surgeries or failure to intervene in those with a missed diagnosis.” – by Casey Tingle
Disclosure: Wolff reports no relevant financial disclosures.
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