Tc-99 m diethylenetriamine-pentaacetic acid (DTPA): is it reliable for assessment of methotrexate-induced cumulative effect on renal filtration in rheumatoid arthritis patients?

Methotrexate (MTX) is commonly employed as the initial DMARD used for the treatment of rheumatoid arthritis (RA). We aimed to contribute to the safety profile of MTX by assessing its cumulative effect on renal filtration. A total of 52 RA adult female patients with normal baseline serum creatinine and GFR at the initial diagnosis of the disease were included. Group 1 (G1) included 30 patients (mean age 40.4 ± 4.4 years) on MTX and NSAIDS, while 22 RA patients (mean age 38.5 ± 8.2 years) who received NSAIDs only served as control group (G2). Renal function was assessed by GFR measurement using technetium diethylenetriamine-pentaacetic acid (Tc-99 m DTPA) at a point of the study time corresponding to disease duration. Twenty-one out of thirty (70 %) in G1 showed reduced GFR compared to 6/22 (27.3 %) in G2 (P = 0.007), with 3.3 ± 0.5 % annual reduction in GFR. Reduced GFR in G1 showed significant negative correlation with age (r = -0.396, P = 0.005), MTX cumulative dose (r = -0.263, P = 0.049), MTX-intake duration (r = -0.293, P = 0.031) and NSAIDs-intake duration (r = -0.344, P = 0.014). Low-dose MTX has a slow cumulative effect on renal filtration manifested by GFR reduction overtime that could be monitored by Tc-99 m DTPA.