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February 23, 2000

Clinical Diagnosis of Carpal Tunnel Syndrome

Author Affiliations

Phil B.FontanarosaMD, Deputy EditorIndividualAuthorStephen J.LurieMD, PhD, Fishbein FellowIndividualAuthor

JAMA. 2000;283(8):1000-1003. doi:10.1001/jama.283.8.999

To the Editor: Several factors cause biases in the CTS prevalence estimates reported by Dr Atroshi and colleagues1 (at least 1 upward and multiple downward biases); consequently, the accuracy of these estimates is questionable.

The authors used a median-ulnar sensory latency difference of 0.8 milliseconds or longer derived from normal values reported by Kimura2 as their electrophysiological criterion of abnormality. However, the practice parameter for electrodiagnostic studies3 cited by the authors in their choice of criterion requires that reference values be obtained with either concomitant studies of a reference population or with previous studies of a reference population in the same laboratory. The Kimura data used by the authors were obtained from a different population in a different laboratory. In fact, Atroshi et al did study an appropriate reference population, that is, asymptomatic respondents to their survey. However, instead of using this reference population to derive the criterion of abnormality to be applied to their test subjects, they applied the Kimura criterion to the asymptomatic responders, yielding an 18.4% rate of supposed subclinical median neuropathy. If the authors had instead appropriately derived their criterion of abnormality from this reference population, their criterion of abnormality would have been significantly higher, yielding lower estimates for the prevalence of CTS. (A criterion of abnormality applied to the reference population from which it was derived is expected to yield 2.5% "abnormal" results for normally distributed populations.)

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