Tc-99m 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 treatment of Rheumatoid arthritis[RA]. We aimed to contribute to the safety profile of MTX by assessing its cumulative effect on renal filtration. Fifty two RA adult females with normal base-line 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 the control group[G2]. Renal function was assessed by GFR-measurement using Technetium diethylenetriamine-pentaacetic acid[Tc-99 m-DTPA] at the point of the study time corresponding to disease duration. 21/30[70%] in G1 showed reduced GFR compared to 6/22[27.3%] in G2[P0.007] with 3.3 ± 0.5% annual reduction of 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 NSAID-intake duration[r = −0.344, P = 0.014]. Low dose MTX has a slow cumulative effect on renal filtration manifested by GFR reduction over time that could be monitored by Tc-99 m DTPA.