Utility of the Neuropathic Pain Symptom Inventory in people with spinal cord injury.

ABSTRACT

STUDY DESIGN: Cohort/psychometric study OBJECTIVES: The primary objective was to determine the psychometric properties and the utility of the Neuropathic Pain Symptom Inventory (NPSI) in subgrouping people with moderate to severe neuropathic pain after spinal cord injury (SCI). SETTING: University-based laboratory in Miami, FL USA. METHODS: Seventy-two people with chronic SCI and neuropathic pain were included in this study. The NPSI, Numeric Rating Scale (NRS), Multidimensional Pain Inventory pain severity and perceived support subscales (MPI-PS and MPI-S, respectively), and the Coping Strategies Questionnaire were administered. The NPSI was administered twice, with a 2-4-week period between measurement sessions. RESULTS: The NPSI total score demonstrated good internal consistency with a Cronbach's alpha of 0.70. The test-retest reliability (intraclass correlations) ranged from 0.65 to 0.73 for the NPSI subscores and 0.79 for the total NPSI score. Further, construct validity was supported by moderate and significant positive correlations with the pain intensity NRS and pain severity subscale of the MPI (MPI-PS) (r > 0.40). Cluster analysis of factor scores derived from NPSI subscales, NRS, and MPI-PS scores revealed three distinct subgroups (1) low-moderate, (2) moderate, and (3) high pain symptom severity with mean NPSI sum scores of 7.1, 17.5, and 33.8, respectively. CONCLUSION: The NPSI demonstrated good psychometric properties in people with neuropathic pain after SCI. Moreover, it has utility for establishing pain symptom phenotypes.