• Timothy W Victor, Mark P Jensen, Arnold R Gammaitoni, Errol M Gould, Richard E White, and Bradley S Galer.
• Endo Pharmaceuticals Inc, Chadds Ford, PA 19317, USA. victor.timothy@endo.com
• Clin J Pain. 2008 Jul 1;24(6):550-5.

ObjectiveTo provide a better empirical understanding of the dimensionality of neuropathic and non-neuropathic pain quality.MethodAn exploratory factor analysis (FA) was performed with baseline pain quality data [assessed using the Pain Quality Assessment Scale (PQAS)] from patients with osteoarthritis of the knee (n=368) and low back pain (n=455) who had participated in a series of analgesic clinical trials. The results of the FA were then confirmed in a sample of patients with neuropathic pain secondary to carpal tunnel syndrome (n=138). Comparisons between the diagnostic groups on scale scores derived from the FA results were also made using t tests.ResultsThree clear pain quality factors emerged that seemed to represent (1) paroxysmal pain sensations (PQAS descriptors: shooting, sharp, electric, hot, and radiating), (2) superficial pain (itchy, cold, numb, sensitive, and tingling), and (3) deep pain (aching, heavy, dull, cramping, and throbbing). The PQAS tender pain item did not load strongly on any of the 3 factors.DiscussionThe findings support the hypothesis that pain qualities cluster into distinct groups. If replicated in additional samples, the pain quality domains identified may provide clinicians and researchers with a useful way to summarize data from pain quality measures, and may also provide meaningful end points that would allow for treatment differentiation between various pharmacologic entities.

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