Preliminary validity data on a screening tool to differentiate pain subtypes in persons with spinal cord injury

Persons with spinal cord injury (SCI) experience two main subtypes of pain: nociceptive and neuropathic. There is not currently a diagnostic or screening instrument that would help the clinical researcher determine which subtype of pain an individual is experiencing. Existing neuropathic pain scales are chiefly normed on individuals with peripheral neuropathic pain, and some of the items on these scales do not "work" for spinal cord injury neuropathic pain. The IASP proposed an SCI pain classification scheme which is descriptive in nature, and has been used to guide clinicians and researchers in diagnosing subtype of pain. However the psychometrics of the scheme are not optimal, and it does not provide any discrete method for a non-experienced clinician to classify pain subtypes. We thought it would be helpful if a screening instrument was created that could reliably differentiate nociceptive from neuropathic SCI pain, and that could be administered by a research assistant. One of our group had developed a series of seven potential screening items reflective of SCI neuropathic pain based on his review of the literature. Experienced pain/SCI clinicians determined whether or not pain sites were neuropathic or nociceptive using the IASP scheme for 92 SCI pain sites as part of a multi-site RCT. A confidence rating was also derived. Research assistants independently administered the seven neuropathic pain screening items. Correlations were calculated between screening item endorsement and the most confident clinical ratings. Four of the seven screening items correlated significantly with clinician judgments of pain subtype. We are completing further analyses on these items to determine if the resulting instrument has adequate validity to be used as a screening measure in studies or in clinical settings where diagnostic judgments as to the type of SCI pain present are needed.