Psychometric validation of the neuropathic pain symptom inventory for its use in Spanish.

CONTEXT: Clinical instruments are required for the assessment of neuropathic pain (NP).
OBJECTIVES: The primary aim of this study was to perform a complete psychometric validation of the Neuropathic Pain Symptom Inventory (NPSI) in Spanish patients.
METHODS: A linguistically validated version in Spanish of the NPSI and other clinical instruments for NP were administered on two occasions separated by at least one month to 548 patients suffering from chronic NP. The authors evaluated the responsiveness, the construct validity, and the internal structure of the NPSI by means of, respectively, receiver operating characteristic (ROC) curves analysis and calculation of reliable change indices, a multitrait-multimethod (MTMM) design, and primary component analysis. Internal consistency and test-retest reliability were evaluated, respectively, by calculating several Cronbach's alpha coefficients and intraclass correlation coefficients of some scores selected appropriately.
RESULTS: The areas under the ROC curves were greater than 0.85. The MTMM design found convergent-discriminant correlations correctly aligned for all NPSI subscores in the first assessment, and for all but paresthesia/dysesthesia subscores in the second assessment. The five components of the NPSI described by its authors were confirmed on one occasion, but the "electric shocks" and "stabbing" items did not associate consistently, as in the original version, the first time the NPSI was administered. All reliability coefficients were above 0.70.
CONCLUSION: The Spanish NPSI has good concurrent and construct validity and is reliable for a wide range of patients with NP. One exception to the original structure was found affecting one item, presumably relating to a cultural feature.