Serum serotonin in rheumatoid arthritis patients: Relation to rheumatoid factor positivity, clinical manifestations and fibromyalgia

Aim of the work: To estimate serum level of serotonin in rheumatoid arthritis (RA) patients and study its relation with various clinical data, radiographic scores and fibromyalgia. Patients and methods: This study involved eighty RA patients divided equally according to rheumatoid factor (RF) positivity. Modified Health Assessment Questionnaire, disease activity score in 28-joints (DAS 28), visual analogue scale of pain, Short Form Health Survey for mental and physical health, fibromyalgia questionnaire, RA Articular Damage score and radiological joint damage by van der Heijde modification were assessed. Serum level for serotonin was measured for all patients. Results: The mean age of seronegative patients was 41.7 ± 10.7 years; 36 females and 4 males and of seropositive (44.9 ± 12.9 years and were 34 females and 6 males). Serum serotonin level was high in RA patients compared to control (129.8 ± 99.1 ng/ml vs 79.6 ± 54.5 ng/ml respectively, p = 0.001). Serum serotonin was higher in seropositive than seronegative (155.9 ± 93.2 vs 101.5 ± 99.4 ng/ml respectively, p = 0.007). Fibromyalgia syndrome (FMS) was associated with a significant lower serotonin level in both groups (p < 0.005). High serotonin level was associated with combined disease modifying antirheumatic drugs (p = 0.04) in seronegative patients. A lower serotonin level was associated with corticosteroids administration and dry eye (p = 0.03, p = 0.004 respectively) in seropositive cases. A significant correlation was present between serotonin level with erythrocyte sedimentation rate, vitality energy and mental health (r = 0.4, p < 0.05) in seropositive patients. Conclusion: Serum serotonin level was high in RA, especially in seropositive patients. It demonstrated central antidepressant and peripheral pro-inflammatory role. The SSRI could be of benefit only in RA with FMS. Keywords: Rheumatoid arthritis, Serotonin, Rheumatoid factor positivity, Fibromyalgi