Early diagnosis of carpal tunnel syndrome: Comparison of digit 1 with wrist and distoproximal ratio

Khema R. Sharma, Francisco Rotta, Jose Romano, D. Ram Ayyar

Research output: Contribution to journalArticlepeer-review

9 Scopus citations

Abstract

Our objective in this study was to compare the sensitivity and specificity of the median sensory nerve conduction velocity (SNCV) from digits to wrist with those of the distoproximal (D/P) ratio of the median SNCV from palm to digit 3/palm to wrist in the diagnosis of mild carpal tunnel syndrome (CTS by using a receiver operating characteristic (ROC) curve. To achieve this objective, we studied prospectively (January 1997-October 1998) 370 patients referred for CTS. One hundred forty-two patients (38.4%) with moderate to severe CTS and 15 patients (4.1%) with multiple (≥3) compressive neuropathies in upper limbs with subclinical peripheral neuropathy were excluded. The remaining 213 patients (302 hands with mild CTS; 167 women; mean age, 50 y ± 12 y) and 38 controls (71 hands; 25 women; mean age, 47 y ± 13 y) had median and ulnar nerve conduction studies. ROC curves were constructed for median SNCV digit 1 to wrist and median SNCV D/P ratio from the patients' and controls' data. The median SNCV at ≤45.9 m/s, corresponding to an optimal cutoff point on ROC curve, discriminated 89.5% of mild CTS from controls with specificity of 98.6%. The median D/P ratio at ≥1.12, corresponding to an optimal cutoff point on ROC curve, discriminated 67.2% of mild CTS from controls with specificity of 97.2%. Of the 10.3% (31/302) of hands in which digit 1 to wrist was within normal limits at the selected optimal cutoff value (≤45.9 ms), 7% (21/302) had an abnormal D/P ratio (≥1.12), and 3.3% (101/302) had a normal electrophysiologic examination. The likelihood ratio (true-positive ratio to false-positive ratio, assessing the discriminative power of a test) of the median SNCV digit 1 to wrist, at an optimal point on ROC curve (63.9), was higher than that of the median SNCV D/P ratio (23.9, χ2 = 36.9, P < .001). These findings suggest that the median SNCV digit 1 to wrist is more sensitive than the median SNCV D/P ratio in the diagnosis of mild CTS.

Original languageEnglish (US)
JournalNeurology and Clinical Neurophysiology
Volume2001
DOIs
StatePublished - 2001

Keywords

  • Carpal tunnel syndrome
  • Digit one
  • Distoproximal ratio
  • Early diagnosis
  • Median sensory nerve conduction velocity
  • Receiver operating characteristic curve
  • Sensitivity
  • Specificity

ASJC Scopus subject areas

  • Neuroscience(all)
  • Medicine(all)

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