Obtaining Tissue Diagnosis Before Initiation of Corticosteroids

To the Editor: In the December 2008 issue of Mayo Clinic Proceedings, Maripuri and Fervenza¹ thoroughly discuss the case of a patient with likely rapidly progressive glomerulonephritis, who had a creatinine level of 2.1 mg/dL (with no previously known renal failure), proteinuria, and dysmorphic red blood cells in the urinary sediment. Regarding management, the authors state that “empirical treatment without obtaining a tissue diagnosis would be inappropriate given the potential toxicities involved with the use of high-dose corticosteroids and CYC [cyclophosphamide].”¹ That strategy seems to be discordant with the standardized treatment of rapidly progressive glomerulonephritis, which dictates immediate therapy to avoid progression to end-stage renal disease.^2-3 In cases of diagnostic uncertainty, empirical treatment is indicated for all diagnoses whose probability exceeds their therapeutic threshold (which is the probability of a particular disease above which empirical treatment should be initiated).⁴ For rapidly progressive glomerulonephritis, the therapeutic threshold is very low because the potential harm of corticosteroids is relatively minor compared with the greater effect on survival due to initiation of corticosteroids to prevent end-stage renal failure.⁵