The Current Perception Threshold Test Differentiates Categories of Mechanical Neck Disorder

Study Design Cross-sectional discriminative analysis. Objective To determine whether current perception threshold (CPT) can differentiate between categories of patients with mechanical neck disorders (MNDs). Background Neck pain is the third most common musculoskeletal disorder, affecting a third of all adults each year. It can present as neck pain without musculoskeletal signs; neck pain with musculoskeletal signs but no neurological signs; neck pain with neurological signs. CPT testing can assess altered sensory perception that may reflect neurological changes. Methods Patients with MNDs (n=106) were classified into 3 groups based on a standardized musculoskeletal examination process performed by an experienced physiotherapist blinded to CPT scores. The 3 groups were defined as: MND-I, neck pain without musculoskeletal signs (n=60); MND-II, neck pain with musculoskeletal signs (n=29); MND-III, neck pain with neurological signs (n=17). A rapid protocol of CPT testing was performed at 3 frequencies (5, 250, 2000 Hz), using 3 dermatomal locations on the hand. A 1-way ANOVA with post hoc comparison and effect sizes were calculated to compare the mean CPT score between the groups. A binary logistic regression model was used to predict probability of higher CPT in MND-III and used to create a receiver operating characteristic (ROC) curve. Results Mean CPT differed significantly across the 3 MND groups (MND-I, 9.7; MND-II, 10.6; and MND-III, 11.8; P < .001, η² = .6). Post hoc comparisons indicated differences between MND-I and MND-II (P = .05) and between MND-II and MND-III (P = .01), that were large effect sizes (MND I versus II, d = 1 and MND II versus III, d = 2.2). CPT testing was able to distinguish between MND II and III when a threshold value of greater than 11 was used to indicate MND-III. The predicted probability of abnormal CPT in MND-III had an estimated 73% sensitivity and 81% specificity; the odds ratio was 11.5 (P =.001) for the differentiation capacity of CPT between MND-II and III with a cut-off of 11. The area under the ROC curve (AUC) was .84 (95% CI =.72 to .96, P < .001). Conclusions CPT testing has moderate discriminatory accuracy, specificity, and sensitivity for classification of MND categories into neck pain with or without neurological signs. J Orthop Sports Phys Ther, Epub 10 May 2014. doi:10.2519/jospt.2014.5691.