Background Composite indices DAS-28 (Disease Activity Score, assessing 28 joints), SDAI (Simplified Disease Activity Index), CDAI (Clinical Disease Activity Index) are widely used instruments for the assessment of disease activity in the patients (pts) with rheumatoid arthritis (RA), but they may not be sufficient to evaluate activity in cases of RA associated with chronic pain syndromes such as fibromyalgia (FM).

Objectives To examine the FM impact on disease activity composite indices in pts with RA.

Methods We examined 120 pts (29 males, 91 females) with RA on the presence of concomitant FM according the ACR criteria (1990). All the patients were examined by the same rheumatologist, assessing TJC (tender joint count), SJC (swollen joint count) and TPC (tender point count). Laboratory parameters included erythrocyte sedimentation rate (ESR), C-reactive protein (CRP), rheumatoid factor (RF) and anti-citrullinated peptide antibody (ACPA). RA activity was evaluated by three composite indices (DAS-28, SDAI and CDAI) and functional disability by Health Assessment Questionnaire (HAQ).

Results The diagnosis of FM was established in 25 (20.8%) pts with RA (RAF), 4 men and 21 women. RA and RAF pts did not differ significantly in sociodemographic characteristics (age, eduacation, marital status, RA duration), laboratory inflammatory markes, RF and ACPA seropositivity. RAF pts in comparison to RA pts were found to reach significantly higher scores in all three composite indices (DA-28 5.35±1.1 vs. 3.67±1.4, p<0.0001; SDAI 31.8±10.9 vs. 13.5±10.8, p<0.0001; CDAI 29.6±10.7 vs. 11.8±9.4, p<0.0001) and in disability level (HAQ 1.83±0.64 vs. 0.87±0.76, p<0.0001). Detailed analysis revealed that TJC and VAS-GH (patient’s global health on a 100 mm visual analog scale) contributed mostly to the disease activity diferencies in RA and RAF, but doctor’s global health VAS was also significantly increased in pts with RAF in comparison to RA.

Conclusions Rheumatologists, using disease activity composite indices in a daily clinical practice and clinical trials, should be aware of the limitations when these indices do not reflect real inflammatory activity but result from measurements dependent on an individual patient’s pain perception.

Disclosure of Interest None Declared