OBJECTIVE: To evaluate the diagnostic utility of nerve conduction studies (NCSs) by examining a population with a high pretest probability of carpal tunnel syndrome (CTS), including bilaterally and unilaterally symptomatic patients. DESIGN: Comparison of the results of NCSs with the results of prospective, pre-NCS, self-administered questionnaires of patients with clinical diagnoses of CTS referred for confirmatory NCSs. SETTING: A tertiary care hospital neuro-electrophysiology laboratory. PARTICIPANTS: The study population consisted of 211 patients, 156 (73.9%) of whom were female. Population mean (range) age was 46.7 (21 to 88) years. Mean (range) symptom duration was 29.3 (1 to 300) months. MAIN OUTCOME MEASURES: Patient-reported symptom localization and NCS results. RESULTS: Results of NCSs were normal in 83 (39.3%) patients, were consistent with CTS in 121 (57.3%) patients, and suggested non-CTS abnormalities in 7 (3.3%) patients. Bilateral symptoms were reported by 139 (65.9%) patients, and isolated unilateral symptoms were reported by 72 (34.1%) patients. Those reporting bilateral symptoms had the highest agreement with NCS results at 38.8%. Unilateral NCS abnormalities were seen in 18.0% of those reporting bilateral hand symptoms. Discordant findings, either bilateral or opposite-side neuropathies, were seen in 25.6% of those reporting isolated right-sided symptoms, and in 55.2% of those reporting isolated left-sided symptoms. Based on these data the sensitivity of the NCS results was 49.1%, with a specificity of 62.5%. The positive predictive value was 86.4%, and the negative predictive value was 20.2%. Overall accuracy was 51.4%. Likelihood ratios were 1.3 with positive results, and 0.8 with negative results. CONCLUSION: In our study population NCS results did little to alter the pretest probability of CTS. Physicians using NCSs for verification of clinical diagnosis should be aware of potential limitations.
OBJECTIVE: To evaluate the diagnostic utility of nerve conduction studies (NCSs) by examining a population with a high pretest probability of carpal tunnel syndrome (CTS), including bilaterally and unilaterally symptomatic patients. DESIGN: Comparison of the results of NCSs with the results of prospective, pre-NCS, self-administered questionnaires of patients with clinical diagnoses of CTS referred for confirmatory NCSs. SETTING: A tertiary care hospital neuro-electrophysiology laboratory. PARTICIPANTS: The study population consisted of 211 patients, 156 (73.9%) of whom were female. Population mean (range) age was 46.7 (21 to 88) years. Mean (range) symptom duration was 29.3 (1 to 300) months. MAIN OUTCOME MEASURES: Patient-reported symptom localization and NCS results. RESULTS: Results of NCSs were normal in 83 (39.3%) patients, were consistent with CTS in 121 (57.3%) patients, and suggested non-CTS abnormalities in 7 (3.3%) patients. Bilateral symptoms were reported by 139 (65.9%) patients, and isolated unilateral symptoms were reported by 72 (34.1%) patients. Those reporting bilateral symptoms had the highest agreement with NCS results at 38.8%. Unilateral NCS abnormalities were seen in 18.0% of those reporting bilateral hand symptoms. Discordant findings, either bilateral or opposite-side neuropathies, were seen in 25.6% of those reporting isolated right-sided symptoms, and in 55.2% of those reporting isolated left-sided symptoms. Based on these data the sensitivity of the NCS results was 49.1%, with a specificity of 62.5%. The positive predictive value was 86.4%, and the negative predictive value was 20.2%. Overall accuracy was 51.4%. Likelihood ratios were 1.3 with positive results, and 0.8 with negative results. CONCLUSION: In our study population NCS results did little to alter the pretest probability of CTS. Physicians using NCSs for verification of clinical diagnosis should be aware of potential limitations.
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