Accuracy of the Standard and Distal-to-Proximal Sequence of the Upper Limb Neurodynamic Test 1 for the Diagnosis of Carpal Tunnel Syndrome: The Role of Side-to-Side Comparisons

<b>Background/Objective</b>: This study aimed to evaluate the diagnostic accuracy of two upper limb neurodynamic test 1 (ULNT1) sequences for detecting carpal tunnel syndrome (CTS) in patients with unilateral symptoms. The standard sequence (ULNT1-STD) and a distal-to-proximal sequence (ULNT1-DIST) were investigated. A local-initiated sequence may facilitate symptoms reproduction in CTS, and comparing the affected side with the unaffected side could improve the detection of altered median nerve mechanosensitivity when symptoms are not directly reproduced. <b>Methods</b>: A total of 134 consecutive patients with clinically suspected unilateral CTS were recruited. Nerve conduction studies were used as a reference test. <b>Results</b>: When considering only symptom reproduction as the criterion for a positive test, ULNT1-STD showed a sensitivity of 0.398 and a specificity of 0.780 (positive likelihood ratio [+LR]: 1.81; negative likelihood ratio [-LR]: 0.77); whereas ULNT1-DIST demonstrated a sensitivity of 0.548 with a specificity of 0.732 (+LR: 2.04; -LR: 0.62). When a positive test was defined by symptom reproduction or inter-limb asymmetry (in range of motion or sensory response), ULNT1-STD showed an improved sensitivity of 0.613 but a reduced specificity of 0.537 (+LR: 1.32; -LR: 0.72). In comparison, ULNT1-DIST increased its sensitivity to 0.871 with a specificity of 0.683 (+LR: 2.75; -LR: 0.19). <b>Conclusions</b>: ULNT1-DIST offers better diagnostic accuracy for CTS compared to the ULNT1-STD sequence, especially when interlimb asymmetries in range of motion or sensory response are considered. However, side-to-side comparisons have reduced utility in cases with bilateral symptoms, limiting their application in clinical practice.