Early Diagnosis of Carpal Tunnel Syndrome: Comparison of Digit 1 with Wrist and Distoproximal Ratio

Abstract

Our objective in this study was to compare the sensitivity and specificity of the median sensory nerve conduction velocity (SNCV) from digit 1 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 (> or = 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 < or = 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 > or = 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 (< or = 45.9 ms), 7% (21/302) had an abnormal D/P ratio (> or = 1.12), and 3.3% (10/302) 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, chi2 = 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.

Diagnosis of Carpal Tunnel Syndrome

“…Thirteen published studies were evaluated and met criteria for review compared with a reference standard of signs, symptoms, and one electrodiagnostic test. Twelve of these studies [15][16][17][18][19][20][21][22][23][24][25][26] were level IV and one 27 was level II. The reference standard used included signs, symptoms, and a different electrodiagnostic test than the electrodiagnostic test being evaluated in the study.…”

Comparación de métodos diagnósticos electrofisiológicos del Síndrome del Túnel Carpiano

“…Con respecto a la velocidad de conducción sensitiva, estudios previos han mostrado mayor sensibilidad en el primer dedo en pacientes con STC leve, pero en la investigación que nos ocupa, no se diagnosticó gravedad del STC y la velocidad de conducción sensitiva resultó fiable con elevada sensibilidad (Sharma et al, 2001).…”

Test-retest reliability of transcarpal sensory NCV method for diagnosis of carpal tunnel syndrome

“…Nowadays, increasing understanding about CTS makes it possible to have these patients in their earlier stages of the disease in electrodiagnostic clinics; however, up to 40% of the patients with typical symptoms may have no electrodiagnostic evidence of CTS. [ 12 ]…”