Global Glomerulosclerosis in Kidney Biopsies With Differing Amounts of Cortex: A Clinical-Pathologic Correlation Study

Abstract Rationale & Objective The number of glomeruli is often used to determine adequacy of a kidney biopsy (e.g., at least 10 glomeruli). It is often assumed that biopsies with limited amounts of cortex are too imprecise for detection of focal pathology. Study Design Clinical-pathological correlation (cross-sectional) Setting & participants Living kidney donors who underwent a needle core biopsy of their kidney at the time of donation. Exposure The amount of cortex biopsied as determined by either the number of glomeruli or the area of cortex on histology. Outcome The percentage globally sclerotic glomeruli (% globally sclerotic glomeruli), density of interstitial fibrosis foci, and the severity of arteriosclerosis were determined. Analytical approach A beta-binomial model assessed how the mean % globally sclerotic glomeruli and patient variability in % globally sclerotic glomeruli differed with number of glomeruli on the biopsy. Additional models assessed the association of interstitial fibrosis and arteriosclerosis with number of glomeruli. Results There were 2,915 kidney donors studied. Fewer glomeruli on biopsy associated with higher mean % globally sclerotic glomeruli and higher patient variability in % globally sclerotic glomeruli. Smaller cortical volume on imaging correlated with both less cortex on biopsy and higher % globally sclerotic glomeruli. Based on a statistical simulation, the probability of patient % globally sclerotic glomeruli ≥10% if the biopsy % globally sclerotic glomeruli ≥10% (positive predictive value) was 45% with 1 to 9 glomeruli versus 31% with 10 or more glomeruli; the negative predictive value was 91% versus 98%. Fewer glomeruli also associated with more interstitial fibrosis and arteriosclerosis. Limitations Study was limited to living kidney donors. Patient variability in % globally sclerotic glomeruli was based on a statistical model as multiple biopsies per patient were not available. Conclusions The amount of cortex on a needle core biopsy is not completely random. Chronic changes from loss of cortex contribute to low amounts of cortex on a kidney biopsy specimen.