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'Scratch test' detects carpal tunnel syndrome.

TUCSON, ARIZ. -- A novel test for diagnosing carpal and cubital tunnel syndromes was at least as accurate as conventional tests, according to the findings of a prospective, case-control study.

During the so-called scratch-collapse test, patients perform a simple resistive motor task, such as pressing their extended arms against a clinician, who then lightly scratches the site of peripheral nerve compression. The patient then immediately attempts to repeat the motor task. If the test is positive, there is a brief loss of proximal postural stability, or "collapse," in the arm, Dr. Christine Cheng explained at the annual meeting of the American Association for Hand Surgery.

The test was developed by San Diego orthopedic surgeon Dr. John Beck, based on observations of postural stimulation and muscle control in patients with Parkinson's disease. The exact mechanism is not fully understood. But it is hypothesized that the test is detecting a short circuit or delay in the proximal muscles, said Dr. Cheng of Washington University, St. Louis.

She presented data from a prospective study in which 169 patients and 109 controls were evaluated for carpal and cubital tunnel syndromes using Tinel's sign, Phalen's test, elbow flexion, and the scratch-collapse test. Electrodiagnostic studies were used to confirm the diagnosis.

Sensitivity of the scratch-collapse test in subjects with carpal tunnel syndrome was 75%, compared with 37% for Tinel's sign and 47% for Phalen's test. Specificity was 62%, 75%, and 66%, respectively. Accuracy was 72%, 47%, and 54%.

Sensitivity of the scratch-collapse test in subjects with cubital tunnel syndrome was 83%, compared with 65% for Tinel's sign and 54% for elbow flexion. Specificity was 82%, 86%, and 81%, respectively. Accuracy was 82%, 77%, and 69%.

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Title Annotation:Musculoskeletal Disorders
Author:Wendling, Patrice
Publication:Family Practice News
Article Type:Brief article
Geographic Code:1USA
Date:Apr 1, 2006
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