In patients with rheumatoid arthritis (RA), the presence of fibromyalgia strongly influences results on the Disease Activity Score assessing 28 joints (DAS28), and the patient-reported components of the DAS28 can be useful to identify comorbid fibromyalgia, according to results published in Rheumatology International.
The study included 292 participants with RA who underwent clinical and clinimetric assessment and completed the DAS28 and the derived DAS28 patient-reported components (DAS28-P), which was calculated by rearranging the components of the DAS28-ESR formula. Participants were grouped according to the presence of fibromyalgia, and student parametric t-tests or Mann-Whitney nonparametric U tests were used to determine between-group differences. Receiver operating characteristic (ROC) curve analysis was used to test the ability of the DAS28-P to distinguish between participants with RA and those with fibromyalgia and RA.
Mean patient age was 63 years with a mean disease duration of 11.6 ± 8.5 years.
The researchers identified 43 participants (14.7%) with concomitant fibromyalgia. These participants had significantly higher tender joint count (P <.001), pain numerical rating scale, global health status (P =.007), and DAS28 scores (P =.006) compared with participants without fibromyalgia.
The results indicated that participants with fibromyalgia and RA had significantly higher DAS28-P values compared with participants without fibromyalgia (0.68 ± 0.09 vs 0.58 ± 0.06; P < 0.001).
The researchers found that the discriminatory power of the DAS28-P was very good (area under the ROC of 0.858, optimal cut-off value of 0.631).
“Patients [with RA] frequently have associated [fibromyalgia] and, therefore, report persisting pain even when inflammation is well controlled,” the researchers wrote. “DAS28 of patients whose assessments are discordant with those of their physicians may not accurately reflect disease activity.”
Salaffi F, Di Carlo M, Carotti M, Sarzi-Puttini P. The subjective components of the Disease Activity Score 28-joints (DAS28) in rheumatoid arthritis patients and coexisting fibromyalgia [published online June 28, 2018]. Rheumatol Int. doi:10.1007/s00296-018-4096-z