No association between TNF inhibitor and methotrexate therapy versus methotrexate in changes in hemoglobin A1C and fasting glucose among psoriasis, psoriatic arthritis, and rheumatoid arthritis patients
BACKGROUND: The use of tumor necrosis factor inhibitors (TNFi) has been associated with a reduced incidence of type 2 diabetes mellitus.
OBJECTIVE: To compare changes in hemoglobin A1C and fasting glucose for patients exposed to TNFi.
METHODS: In this retrospective cohort study, patients with at least 3 recorded diagnosis codes for psoriasis, psoriatic arthritis, or rheumatoid arthritis between January 1, 2004 and July 31, 2011. Patients were Kaiser Permanente Southern California members for at least 1 year prior to the index date.
RESULTS: For hemoglobin A1C, there were 344 patients in the MTX cohort, and 118 patients in the TNFi+MTX cohort. In the covariate adjusted main effects ANCOVA model, the TNFi+MTX cohort had a lower mean change in hemoglobin A1C of -0.18mg/dL (95% CI: -0.35, -0.01) compared to the MTX cohort, although the difference is small and this model was not complete as there were significant interactions. For fasting glucose, there were 524 patients in the MTX cohort, and 121 patients in the TNFi+MTX cohort. In the covariate adjusted main effects ANCOVA model, change in fasting glucose was not significantly different between groups: -0.58 mg/dL (95% CI: -5.05, 3.88) for the TNFi+MTX cohort compared to the MTX cohort, although this model was not complete as there was a significant interaction.
CONCLUSIONS: The use of TNF inhibitors with MTX was not associated with a significant difference in the change of hemoglobin A1C or fasting glucose compared to MTX alone.