Reliability of two-point discrimination test in carpal tunnel syndrome patients

Objectives: To evaluate the reliability (intra and inter) of two-point discrimination (2PD) test in carpal tunnel syndrome (CTS) patients. Participants: Eighty-six adults with unilateral right hand CTS. Methods: Two examiners performed measurements of 2PD sensation (using Dellon discriminator) on the first three fingers on both hands. The first examiner performed three series of measurements at 1-minute intervals. After 7 days, measurements were repeated by the same examiner (intra-rater). For inter-rater reliability, the examination (by second examiner) was also repeated after 7 days. Results: For the first measurement, inter-rater reliability (ICC2,1) at the affected site ranged from 0.96 to 0.97; values at the non-affected site ranged from 0.79 to 0.89. Analysis of the averages of two measurements (ICC2,2) yielded values at the affected site of 0.98; values at the non-affected site ranged from 0.92 to 0.94. The average of two measurements reduces the smallest detectable difference (SDD) value < 1 mm in all cases. Intra-rater reliability was at least good for all tested fingers for the first measurement, but to record SDD < 1 mm it is necessary to use an average of the first two measurements. Conclusions: The execution of two repeated measurements provides adequate reliability in measurements of 2PD test in CTS patients. For clinical trials, we recommend using at least the average of two measurements of 2PD, which reduce SDD (below 1 mm). This may be particularly important in assessing the effectiveness of therapy.