- Elevated liver enzyme tests among patients with rheumatoid arthritis or psoriatic arthritis treated with methotrexate and/or leflunomide. Curtis, J.R., Beukelman, T., Onofrei, A., Cassell, S., Greenberg, J.D., Kavanaugh, A., Reed, G., Strand, V., Kremer, J.M. Ann. Rheum. Dis. (2010)