Strategies for analyzing nerve conduction data: superiority of a summary index over single tests

Muscle Nerve. 1998 Sep;21(9):1166-71. doi: 10.1002/(sici)1097-4598(199809)21:9<1166::aid-mus7>;2-5.


We compared three strategies for diagnosing carpal tunnel syndrome: using a single test; requiring one, two, or three of three tests to be abnormal; or utilizing a single summary variable incorporating data from three tests. Sixty-five hands of subjects without clinical carpal tunnel syndrome (CTS) were compared with 66 hands with clinical CTS. Three latency differences were measured: median-ulnar (8 cm) midpalmar orthodromic (palmdiff); median-ulnar ring finger (14 cm) antidromic (ringdiff); and median-radial thumb (10 cm) antidromic (thumbdiff). The combined sensory index (CSI) was the sum of these three differences. Sensitivity for the tests was palmdiff 69.7%, ringdiff 74.2%, thumbdiff 75.8%, and CSI 83.1%. Specificity was 95.4-96.9%. Requiring one, two, or three of three tests to be abnormal yielded sensitivities of 84.8%, 74.2%, or 56.1%, respectively, but specificities of 92.3%, 98.5%, and 100%, respectively. We conclude that a combined index improves diagnostic classification over use of single test results.

Publication types

  • Comparative Study

MeSH terms

  • Carpal Tunnel Syndrome / diagnosis*
  • Discriminant Analysis
  • Hand / innervation
  • Humans
  • Neural Conduction / physiology*
  • Neurophysiology / methods*
  • Prospective Studies
  • Reaction Time / physiology
  • Reference Values
  • Sensitivity and Specificity