Fatigue in rheumatoid arthritis and its relation to interleukin-6 serum level

Patients and methodsThe study included 30 patients with RA diagnosed according to the 2010 ACR-EULAR classification criteria for RA and 15 healthy controls. Patients were included if they were above 18 years and fulfilled a score ?6 over 10 of the 2010 ACR-EULAR classification criteria for RA. Disease activity was assessed using 28 joint disease activity score (DAS28), erythrocytes sedimentation rate (ESR), C-reactive protein (CRP). Fatigue was assessed with the Bristol Rheumatoid Arthritis Fatigue Multidimensional Questionnaire (BRAF-MDQ) and serum IL-6 level was measured in patients and controls.ResultsThe BRAF-MDQ was significantly higher among patients (mean = 50.6 ± 15.2) than controls (mean = 7.8 ± 3.7) (p < 0.001). Patients’ mean IL-6 serum level was 35.05 ± 21.23 pg/ml and 4.72 ± 3.09 pg/ml among control subjects (p < 0.001). DAS 28 ranged between 4.33 and 7.67, mean 1st hour ESR was 43.57 mm and CRP was positive in 76.7% of patients. Significant correlations were found between BRAF-MDQ score and serum IL-6 level (r = 0.947, p < 0.001), ESR (r = 0.509, p < 0.001) as well as CRP positivity (r = 0.411, p = 0.005) in RA patients. Serum IL-6 level correlated with ESR (r = 0.463, p < 0.001) and CRP (r = 0.376, p = 0.01) among patients.ConclusionFatigue is a common symptom and scores higher among RA patients than healthy controls and should be measured in all RA patients with simple fatigue questionnaires matching with different cultures. Fatigue becomes more prominent as serum IL-6 level increases independently of the disease duration and activity.