Research designs considerations for chronic pain prevention clinical trials: IMMPACT recommendations

Although certain risk factors can identify individuals who aremost likely to develop chronic pain, few interventions to prevent chronic pain have been identified. To facilitate the identification of preventive interventions, an IMMPACTmeeting was convened to discuss research design considerations for clinical trials investigating the prevention of chronic pain. We present general design considerations for prevention trials in populations that are at relatively high risk for developing chronic pain. Specific design considerations included subject identification, timing and duration of treatment, outcomes, timing of assessment, and adjusting for risk factors in the analyses.We provide a detailed examination of 4 models of chronic pain prevention (ie, chronic postsurgical pain, postherpetic neuralgia, chronic low back pain, and painful chemotherapy-induced peripheral neuropathy). The issues discussed can, inmany instances, be extrapolated to other chronic pain conditions. These examples were selected because they are representative models of primary and secondary prevention, reflect persistent pain resulting from multiple insults (ie, surgery, viral infection, injury, and toxic or noxious element exposure), and are chronically painful conditions that are treated with a range of interventions. Improvements in the design of chronic pain prevention trials could improve assay sensitivity and thus accelerate the identification of efficacious interventions. Such interventions would have the potential to reduce the prevalence of chronic pain in the population. Additionally, standardization of outcomes in prevention clinical trials will facilitate meta-analyses and systematic reviews and improve detection of preventive strategies emerging from clinical trials

Idiopathic distal sensory polyneuropathy: ACTTION diagnostic criteria

Objective: To present standardized diagnostic criteria for idiopathic distal sensory polyneuropathy (iDSP) and its subtypes: idiopathic mixed fiber sensory neuropathy (iMFN), idiopathic small fiber sensory neuropathy (iSFN), and idiopathic large fiber sensory neuropathy (iLFN) for use in research. Methods: The Analgesic, Anesthetic, and Addiction Clinical Trial Translations, Innovations, Opportunities and Networks (ACTTION) public-private partnership with the Food and Drug Administration convened a meeting to develop consensus diagnostic criteria for iMFN, iSFN, and iLFN. After background presentations, a collaborative, iterative approach was used to develop expert consensus for new criteria. Results: An iDSP diagnosis requires at least one small fiber (SF) or large fiber (LF) symptom, at least one SF or LF sign, abnormalities in sensory nerve conduction studies (NCS) or distal intra-epidermal nerve fiber density (IENFD), and exclusion of known etiologies. An iMFN diagnosis requires that at least one of the above clinical features is SF and one clinical feature is LF. Diagnostic criteria for iSFN require at least one SF symptom and at least one SF sign with abnormal IENFD, normal sensory NCS, and the absence of LF symptoms and signs. Diagnostic criteria for iLFN require at least one LF symptom and at least one LF sign with normal IENFD, abnormal NCS, and absence of SF symptoms and signs. Conclusions: Adoption of these standardized diagnostic criteria will advance research and clinical trials and spur development of novel therapies for iDSPs.