Abstract

ABSTRACT:
BACKGROUND:
Melatonin is a pineal gland hormone with complex roles in the pathogenesis of autoimmune disorders. Immune abnormalities and disturbed endocrine secretion have been reported in patients with systemic sclerosis (SSc). A possible role of melatonin in pathogenesis of SSc patients might be present
OBJECTIVE:
To assess the predictive utility of serum melatonin in diagnosis of SSc patients.
METHODS:
A case-control study conducted at Rheumatology Unit of Baghdad Teaching Hospital-Medical City from November 2015 to April 2016 on 40 SSc patients diagnosed according to the 1980 criteria for classification of systemic sclerosis or 2013 American College of Rheumatology/European League Against Rheumatism for the classification of systemic sclerosis criteria and compared with 40 healthy controls matched in age, sex, and body mass index. Patients with overlapping other inflammatory arthritis or connective tissue disease or autoimmune diseases were excluded. Serum melatonin was measured in both groups by enzyme-linked immunosorbent assay (ELISA).
RESULTS:
Mean level of serum melatonin concentration was significantly lower in patients compared with controls (Mean ± SEM of patients was 602.9 ± 30.69 vs 782.1 ± 43.66 pg/ml for controls, p=0.001). The optimum cut-off value of serum melatonin that differentiate between patients and controls was ≤ 810.8 pg/ml (AUC=0.72, p=0.0005). Validity of serum melatonin at the optimum cutoff value showed highest level of accuracy (75%) with sensitivity 87.5% and specificity 62.5% and if the test was positive and the clinical suspicion of prestest probability was 50% then we have 70% confidence that the patient has systemic sclerosis [ Positive predictive value (PPV) at pretest 50%=70%]. However, this confidence will increase to 95.5% if the clinical suspicion of pretest probability was 90% (PPV at pretest probability 90%=95.5%). Also, if the test was negative then we can exclude the disease with 97.8% with confidence [Negative predictive value (NPV) =97.8%].
CONCLUSION:
Serum melatonin was a valid measure to diagnose SSc.