Elucidating the Effects of Methotrexate Therapy on Serum Cytokeratin-18 Levels in Rheumatology

Background: CK-18 is a serological marker of apoptosis that has been widely associated with fibrosis and steatosis in NASH. Many studies have showed association CK-18 levels with NAFLD. To date, there is a profound lack of rheumatology studies on the effect of MTX therapy with regard to CK-18 levels. The relationship between CK-18 levels and cumulative MTX dose, MTX treatment duration, weekly MTX dose is not available in the literature. Objectives: The main purpose of this study was to determine the relationship between serum cytokeratin-18 (CK-18) and cumulative methotrexate dose in rheumatology patients on methotrexate (MTX) therapy. Besides, we studied the correlations between CK-18 and clinical parameters including age, disease duration , duration of MTX therapy, cumulative steroid dose and biochemical parameters such as alanine transaminase (ALT) and aspartate aminotransferase AST). Methods : We recruited 79 rheumatology patients on methotrexate (MTX) therapy as MTX group and 38 patients not on MTX therapy as non-MTX group . All subjects were tested for their serum CK-18 levels using an enzyme-linked immunosorbent assay (ELISA) test. We identified 20 patients with the highest CK-18 levels and 20 patients with the lowest CK-18 levels and had ultrasound liver performed on them. Results : The median serum CK-18 levels were marginally higher among the patients on MTX (1.20 ng/mL [0.19-37.15]) compared to the non-MTX group (1.17 ng/mL [0.37-34.32]). There was a significantly positive relationship between serum CK-18 levels and cumulative MTX dose (r = 0.329, p = 0.003) and total duration of MTX therapy (r = 0.284, p = 0.011). Apart from the above-mentioned variables, the CK-18 levels in MTX group significantly correlated with age (r = 0.265, p = 0.018), ALT (r = 0.440, p = <0.001) and AST (r = 0.478, p= 0.004). Ultrasound liver findings showed median CK-18 levels was higher among patients with abnormal liver findings although statistical significance was not reached. Conclusion : Among patients on MTX therapy, serum CK-18 levels correlated positively with cumulative MTX dose , total duration of MTX treatment , ALT and AST levels. These findings are preliminary and requires validation by future studies in the field of rheumatology.