Computational simulation of renal biopsy accuracy in focal segmental glomerulosclerosis.

The goal of this study was to estimate the diagnostic and prognostic accuracy of renal biopsies in focal segmental glomerulosclerosis (FSGS), accounting for the focal nature of affected glomeruli. Computational simulations were performed on a total of 138,600 virtual kidneys, across a range of FSGS involvement. Simulations were designed to address the diagnostic accuracy of renal biopsies, and the biopsy characteristics required to reflect accurately the true degree of involvement of FSGS in the entire kidney or just the juxtamedullary (JM) region. The diagnostic accuracy of renal biopsies for the detection of at least one FSGS glomerulus exceeded 80% when 10-20% of the kidney was affected by FSGS. Hundreds to thousands of biopsy glomeruli were required to characterize reliably the true extent of FSGS when fewer than 75% of the kidney's glomeruli were affected. Renal biopsies with an average of 20 glomeruli did not accurately reflect the extent of FSGS in kidneys until at least 80% of all glomeruli in the kidney were affected. Targeting JM glomeruli did not result in significant improvements in the prognostic performance characteristics of renal biopsies. These findings suggest that conventional renal biopsies might be inadequate for characterizing the extent of FSGS.