The lumbrical provocation test in subjects with median inclusive paresthesia.

OBJECTIVE

To investigate the value of the Lumbrical Provocation Test (LPT) in predicting carpal tunnel syndrome (CTS) among patients with symptoms suspicious for CTS.

DESIGN

Prospective unigroup technique with blinded comparison of a clinical diagnostic test with 2 commonly used methods of diagnosing CTS: electrodiagnosis and a hand diagram.

SETTING

Outpatient veterans referred by a heterogeneous group of specialists and generalists to a Veterans Affairs medical center electrodiagnostic laboratory.

PATIENTS: Ninety-six consecutive patients who were referred to the electrodiagnostic laboratory with median inclusive paresthesia were evaluated.

INTERVENTIONS: LPT: hold hand as fist for 1 minute (to evaluate changes in paresthesia); electrodiagnostic evaluations: median and ulnar mixed nerve, antidromic sensory, and motor latencies; and hand symptom diagram to describe pain.

MAIN OUTCOME MEASURES: Evaluation of symptoms of paresthesia (with or without pain) inclusive of the median nerve distribution distal to the wrist. Prevalence sensitivity, specificity, and positive and negative predictive value of LPT, and electrodiagnosis, and hand diagram tests.

RESULTS

Compared with the findings obtained with electrodiagnosis, the sensitivity of the LPT was.37; specificity,.71; positive predictive value,.59; and negative predictive value,.50. Compared with the findings obtained with the use of the hand diagram as a clinical measure, the sensitivity of the LPT was.43, specificity,.71, positive predictive value,.59, and negative predictive value,.56.

CONCLUSION

The LPT has minimal use in predicting CTS in patients with median inclusive paresthesia compared with 2 commonly used methods of diagnosing CTS.