Outcome Measures in Randomized-controlled Trials of Neuropathic Pain Conditions

Neuropathic pain (NeP) is a prevalent, disabling, multidimensional condition with significant morbidity; however, there seems to be a variable approach in the use of outcome measures in NeP trials. A search of systematic reviews of interventional randomized-controlled trials for NeP was undertaken to examine the range and types of outcome measures used to determine treatment effects. Keywords and MESH searches were conducted in 5 electronic databases from inception to January 31, 2012. Full-text English-language reviews based on various acute and chronic NeP conditions were included. Two independent reviewers screened papers for inclusion, extracted data, and assessed the quality of reviews. Preferred Reporting Items for Systematic reviews and Meta-Analyses (PRISMA) guidelines were used to critically appraise the reviews. A total of 46 studies were identified: the majority of reviews (n=28/46, 61%) scored well on the PRISMA (PRISMA scores of 20-27/27). Change in levels or intensity of pain were used by the majority of studies as the primary outcome measure in intervention studies (n=40/46 studies, 87%). Few studies used a functional outcome measure as either a primary or secondary outcome measure (n=7/46, 15% of studies).

These results show that measures of pain are predominantly used in trials of NeP conditions and highlight the scant usage of functional outcome measures. The lack of standardization for the diagnostic criteria in NeP trials is also an issue that needs requires consideration for future research and guideline development.