There are many types of pain assessments available to researchers conducting clinical trials, ranging from simple, single-item Visual Analog Scale (VAS) questions through extensive, multidimensional inventories. The primary question addressed in this survey of top-tier medical journals was: Which pain assessments are most commonly used in trials? Articles addressing chronic musculoskeletal pain in clinical trials were identified in 7 major medical journals for the year 2003. A total of 50 studies (1476 total original research articles reviewed) met selection criteria, and from these we identified 28 types of pain assessments. Selected studies were classified according to the dimensions of pain assessed, the type of scale and descriptors/anchors used, and the reporting period specified. The most frequently used assessments were the single-item VAS and the Numeric Rating Scale; multidimensional inventories were used infrequently. There was considerable variability in the instructions patients received about the period to consider when evaluating their pain, and many studies provided only cursory information about their assessments in the methods. Overall, it appears that clinical trials use simple measures of pain and that there is no widely accepted standard for clinical pain assessment that would facilitate comparison of outcomes across trials.
Perspective: This review highlights the heterogeneity of pain outcome measures used and the abundance of single-item measures in clinical trials. Although there are many pain outcome measures available to clinical researchers, more consistency in the field should be encouraged so that results between studies can be compared.