Comment on: Kidney disease in RA patients: prevalence and implication on RA-related drugs management: the MATRIX study: reply

Abstract

SIR, We appreciated the letter from Bateman and colleagues [1]. The case they report emphasizes the risk of MTX use in patients with reduced renal function. In fact, their patient with a Stage 4 renal insufficiency at baseline presented with an episode of functional acute renal failure due to dehydration secondary to diarrhoea. In this particular patient with baseline deeply reduced renal function, the further reduction in glomerular filtration resulted in accumulation, overdosage of MTX and metabolites, resulting in a severe haematotoxicity. In addition, we had previously collected and analysed 10 cases of severe or even fatal MTX toxicity in end-stage renal disease (ESRD) patients after very low MTX doses (<7.5mg/week) [2], which further emphasize the risk of MTX in RA patients with renal insufficiency. There is further evidence on the prevalence of renal insufficiency in RA patients. In our MATRIX study, we identified only one patient with Stage 4 kidney disease (Cockcroft and Gault formula) among 106 RA patients treated with MTX (0.9%). Bateman and colleagues reported a prevalence of around 2% of Stage 4 kidney disease among a population of 879 RA patients treated with MTX. As a result, the estimation of renal function on a regular basis in patients with RA, and especially in patients receiving MTX, is crucial. We agree that clinical guidelines should be released on how to manage those patients on MTX regarding the dosage and the specific monitoring.