Reliability Indices, Limits of Agreement, and Construct Validity of the Current Perception Threshold Test in Mechanical Neck Disorder

The objective of this study was to evaluate the reliability and validity of current perception threshold (CPT) tests in patients with mechanical neck disorder (MND). The rapid CPT protocol was performed at 3 frequencies (5, 250, and 2000 Hz) using 3 dermatomal locations (C6−C8) on the hand of patients with MND (n = 106). A subset of patients (n = 34) was reassessed at a second visit to determine the test-retest reliability. The fingertips of both hands were assessed for intertrial reliability. Internal consistencies of CPT between frequencies were calculated from CPT test scores in the most affected hand. The construct validity of CPT was evaluated by correlating the 3 composite scores derived the from the CPT tests with the Neck Disability Index (NDI) and Cervical Spine Outcomes Questionnaire (CSOQ). Intertrial reliability was good to excellent (intraclass correlation coefficient (ICC), 0.73−0.82; P < 0.001). The test-retest reliability of CPT scores was fair to excellent (ICC, 0.47−0.86; P < 0.001). The mean retest difference and the 95% limits of agreement were −0.3 ± 3 for both 2000 and 250 Hz and 0.1 ± 3.9 for 5 Hz. A small to medium-sized correlation was found between CPT and NDI or CSOQ (r = 0.24−0.37). CPT was consistent across occasions and was associated with neck disability.