Validation and reliability of the Neuropathic Pain Scale (NPS) in multiple sclerosis.

Central neuropathic pain occurs in around 28% of patients with multiple sclerosis (MS). The Neuropathic Pain Scale (NPS) has received preliminary validation in peripheral neuropathic pain conditions. The aim of this study was to validate its use in MS central pain syndromes. We administered the NPS to 141 patients with MS, together with the Short Form McGill Pain Questionnaire (SFMPQ), the Hospital Anxiety and Depression Scale (HADS), and Short Form 36 Health Survey (SF-36). Cronbach's alpha was 0.78 (95% CI 0.69; 0.83), implying a high degree of internal consistency. Three factors, "Familiar," "Superficial," and "Alien Perception," were extracted, accounting for 64% of the variance. The NPS 10-item total correlates with: the SFMPQ 15-item total score, rho=0.63 (95% CI 0.49; 0.74), its Visual Analog Scale, rho=0.49 (95% CI 0.33; 0.64), the transformed Pain domain of the SF-36 rho=-0.49 (95% CI -0.63; -0.32), but not with its remaining seven health domains, or with either the HADS anxiety or the depression scores. Limits of agreement for short-term test or re-test reliability of the 100 point NPS total (median 2 days, range 1 to 7) were -12 to 14 and when administered to 78 patients who rated their neuropathic pain the "Same" [median interval 33 days (range 19 to 126), the long-term test or re-test correlation coefficient was 0.71 (95% CI 0.6; 0.79)]. The NPS appears a useful tool in the assessment of neuropathic pain in MS patients and possibly in measuring outcomes of therapeutic interventions.