Development of a neuropathic pain questionnaire

Ongoing efforts to develop mechanisms-based assessment and treatment of chronic pain have been hindered by the lack of assessment tools differentially sensitive to various phenomena underlying different mechanisms of pain. This study describes the development of an assessment instrument intended to measure neuropathic pain based on qualities of pain as they are inferred from pain descriptors. Subjects were 528 chronic pain patients from several clinics. Of these, 149 had strictly neuropathic pain, while 233 had non-neuropathic pain. Subjects completed a 32 item preliminary questionnaire, which asked them to rate their usual pain on multiple descriptors, as well as the degree to which their pain differed in response to various internal and external factors. This preliminary questionnaire was submitted to factor analysis, and this yielded 6 factors. Representatives of each of these factors were combined with additional items that demonstrated significant differences between neuropathic and non-neuropathic pain groups, to yield a 12 item Neuropathic Pain Questionnaire (NPQ). These items were able to differentiate neuropathic pain patients from non-neuropathic pain patients in a holdout sample with 66.6% sensitivity and 74.4% specificity. The newly developed instrument, NPQ, may be used for the initial screening of neuropathic pain patients. It also has the ability to provide a quantitative measure for the descriptors important in the diagnosis and assessment of neuropathic pain. Consequently, it can be used for monitoring of neuropathic pain treatments and as an outcome measure.