Feasibility of a novel functional sensibility test as an assisted examination for determining precision pinch performance in patients with carpal tunnel syndrome

Abstract

To understand the feasibility of a novel functional sensibility test for determining precision pinch performance in patients with carpal tunnel syndrome, this study investigates the validity, sensitivity and specificity of functional sensibility derived from a pinch-holding-up activity (PHUA) test. Participants include 70 clinically defined carpal tunnel syndrome (CTS) patients with 119 involved hands and 70 age- and gender-matched controls. To examine the discriminating ability of the functional sensibility test, the differences in the ability of pinch force adjustments to the inertial load of handling object between CTS and control subjects are analyzed. The results of functional sensibility are correlated with the severity of CTS to establish concurrent validity. The receiver operating characteristic (ROC) curve is constructed to demonstrate the accuracy of the proposed test. The functional sensibility score significantly discriminates the patients and control groups (respectively, 12.94±1.72 vs. 11.51±1.15N in peak pinch force (FPPeak), p<0.001; 2.92±0.41 vs. 2.52±0.24 in force ratio, p<0.001) and is moderately correlated (r = 0.42-0.54, p<0.001) with the results of traditional sensibility tests (touch-pressure threshold and two-point discrimination test). In addition, there is a statistical difference in the results of functional sensibility (p<0.001) among the subgroups of CTS severity based on electrophysiological study. The sensitivity and specificity are 0.79 and 0.76, respectively, for the functional sensibility test. The areas under the ROC curve are 0.85 and 0.80 for the force ratio and FPPeak, respectively. In conclusion, the functional sensibility test could be feasibly used as a clinical tool for determining both the sensibility and precision pinch performance of hands for the patients with CTS.

Figure 1. The experimental procedures and data analysis of this study.

(A): Schematic representation of the pinch-holding-up activity. (B): Data analysis of a functional sensibility test.

Figure 2. Mean (±SD) of force ratio (upper) and FP_Peak (lower) for CTS and healthy groups.

Statistical differences were observed in both the force ratio and FP_peak between CTS and control groups. (Statistical analysis method: mixed effect model; the level of significance was set at p≤0.05).

Figure 3. Mean (±SD) of SWM, M2PD, S2PD and stress determined from SWM result for various grades of CTS severity based on nerve conduction study.

The difference in all of the traditional sensibility tests between each pair of the CTS subgroups did not reach statistical significance. (Statistical analysis method: the mixed effect model with Bonferroni multiple comparisons test; the significance threshold analyses for Bonferroni post hoc test was set at p = 0.008.).

Figure 4. Mean (±SD) of force ratio and FP_Peak for various grades of CTS severity based on nerve conduction study.

There were statistical differences in the results of functional sensibility between each pair of the CTS subgroups except between the subgroup with minimal and mild severity. (Statistical analysis method: the mixed effect model with Bonferroni multiple comparisons test; the significance threshold for Bonferroni post hoc test was set at p = 0.008.).

Figure 5. Constructed ROC curves for functional sensibility and traditional sensibility tests.