Wolfe F and Michaud K (2007) Assessment of pain in rheumatoid arthritis: minimal clinically significant difference, predictors, and the effect of anti-tumor necrosis factor therapy. J Rheumatol 34: 8–18

Researchers from the US have shown that the visual analog pain scale (VAS) is superior to the Medical Outcomes Study Short Form-36 Health Survey (SF-36) scale for assessing pain in patients with rheumatoid arthritis (RA).

Wolfe and Michaud used data from the National Data Bank for Rheumatic Diseases to quantitatively answer questions that will help clinicians and researchers to understand what causes pain, what factors affect the degree of pain suffered, and how the pain can be relieved.

Data from 12,090 patients with RA were analyzed, with demographic variables, treatments, functional status and pain scores recorded. The results showed that, compared with the SF-36 scale, the VAS pain scale was more strongly correlated with every clinical variable measured. The minimal clinically important change for pain in observational studies was defined as 0.5–1.1 units, and the most appropriate cutoff point for an acceptable level of pain was ≤2.0. The level of pain did not change significantly with age or disease duration, but demographic characteristics had a stronger influence, with greater levels of pain recorded in women and ethnic minorities with RA, and lower levels in college graduates with this disease. Overall, 45% of pain variance could be explained by demographic characteristics combined with the regional site of pain. The results also showed that anti-tumor necrosis factor therapy reduced pain by an average of 0.51 units, satisfying the minimal clinically important change criterion.