New results from the Modification of Diet in Renal Disease study: the importance of clinical outcomes in test strategies for early chronic kidney disease.

A formula derived from the Modification of Diet in Renal Disease (MDRD) study in chronic renal disease is widely used to estimate glomerular filtration rate (GFR). Recently a ten-year follow-up of MDRD participants evaluated four tests of kidney function measured at baseline as predictors of important long-term clinical outcomes. Surprisingly, neither formula-estimated GFR nor reference method GFR showed a clear advantage over simple creatinine measurement whereas another test, cystatin C, looked more promising. This raises important points of principle in terms of how the usefulness of test strategies should be assessed. Data on clinical outcomes are an essential ingredient in this process.