Aim: To determine the level of prolactin in the sera of rheumatoid arthritis (RA) patients and to correlate this level with clinically and radiologically evaluated disease activity and severity parameters.
Methods: The study included 30 patients with RA and 20 healthy individuals as controls. All the patients were subjected to clinical and musculoskeletal examination with the assessment of disease activity using the DAS 28 score and disease severity using the Health Assessment Questionnaire (HAQ) and the modified Duke Severity of Illness score (DUSOI).  Larsen score was used to assess radiological severity. Laboratory investigations included measurement of serum prolactin (sPRL) using the Enzyme Linked Immunosorbent Technique (ELISA) technique, a complete blood count (CBC), kidney function tests, measurement of the rheumatoid Factor (RF), antibodies to cyclic citrullinated peptides (anti-CCP), the erythrocyte sedimentation rate (ESR) and the C-Reactive protein (CRP).
Results: RA patients showed a significantly higher median prolactin level when compared to the control group (p < 0.001). The median prolactin level was significantly increased in the positive RF and positive anti-CCP antibodies patients compared to negative cases (p= 0.027 and p= 0.011 respectively). The median prolactin level increased significantly in higher X-ray grades (p= 0.040). The prolactin level showed significant positive correlations with the ESR (p=0.048), DAS28 (p < 0.001), the short HAQ (p <0.001) and the X- ray grading (p=0.042). The prolactin level showed an excellent AUC (AUC=0.926). At a cut-off value of 10.7 ng/mL, its sensitivity was 80%, specificity was 85%, the PPV was 78%, NPV was 92.7%, and the accuracy was 86.5% regarding the discrimination between RA cases and healthy subjects.
Conclusion: sPRL level is suggested to be a marker for RA disease activity and severity being significantly higher in RA patients compared to healthy subjects, being significantly correlating with the disease activity and severity parameters as well as having a striking 80% sensitivity and 85% specificity for diagnosis of RA