Brooks ER, et al. - This inquiry was set up to scrutinize the additive effect of baseline (BL) levels of methylated arginine derivatives (MADs) on directly measured glomerular filtration rate (mGFR) decline per year (ml/min/1.73 m²/year) for a period of up to 4 years in the setting of pediatric with chronic kidney disease (pCKD). An inverse association of higher concentrations of BL MADs with BL mGFR was shown in pCKD. No impact of MADs on the CKD progression rate was apparent.