How Many Glomerular Profiles Must Be Measured to Obtain Reliable Estimates of Mean Glomerular Areas in Human Renal Biopsies?

Abstract

The objective of this study was to investigate the number of glomerular profiles that are required for accurate estimates of mean profile area in a renal biopsy series. Slides from 384 renal biopsies from one center were reviewed. They contained a median of seven glomerular profiles or of four profiles without sclerosis. Profile areas were measured using stereologic point counting. The "true individual mean" for each biopsy was calculated and the "true population mean" for groups of biopsies derived. Individual and population "random sample means" then were calculated from a random sampling of profiles in each biopsy and were compared with true means for the same biopsies. The effect on the true population means of the entire group of biopsies was also assessed, as the minimum number of glomerular profiles that were required for inclusion was changed. In a single biopsy, random sampling of >10 profiles without exclusions and of eight profiles or more without sclerosis reliably estimated the true mean areas. In a group of 30 biopsies, random sampling of five or more glomeruli per biopsy reliably estimated the true population mean. In the aggregate series, inclusion of all 384 biopsies produced the most robust true population mean; the reliability of the estimates decreased as the numbers of eligible biopsies diminished with increasing requisite minimum numbers of profiles per biopsy. We conclude that, while >10 profiles might be needed for reliable area estimates in a single biopsy, far fewer profiles per biopsy can suffice when groups of biopsies are studied. In analyses of groups of biopsies, all available biopsies should be used without consideration of the number of glomerular profiles in each. Stipulation of a specific minimum number of glomeruli in each biopsy for inclusion reduces the power of analyses because fewer biopsies are available for evaluation.

Percutaneous Renal Biopsy of Native Kidneys: A Single-Center Experience of 1,055 Biopsies

“…Biopsies containing only 10 glomeruli have a 35% probability of missing the lesion if the prevalence of diseased glomeruli is 10%, but the probability decreases to 12% if 20 glomeruli are obtained. As a result, 10 glomeruli is the minimum required in a renal biopsy [41,42,43], and 20 glomeruli are preferable. Thus, the use of a 14-gauge automated needle is preferable, while the increasing use of 18-gauge needles stands to jeopardize the diagnostic accuracy of the PRB.…”

Comparative Safety and Efficiency of Five Percutaneous Kidney Biopsy Approaches of Native Kidneys: A Multicenter Study

“…At least 10 glomeruli are recommended to provide an accurate diagnosis and prognosis based on RB [12,13,14]. According to the literature, mean numbers of glomeruli on biopsies vary between 9 and 33 [18] according to needle size [19,20].…”

“…When no glomeruli were available, the biopsy was considered to have failed. In most glomerulopathy classifications, at least 10 glomeruli are required to consider the core biopsy representative and the diagnosis accurate [12,13,14]. Thus, on LM analysis, biopsies were separated into three groups according to the number of glomeruli on tissue fragments: 0 glomeruli, 1–9 glomeruli, and ≥10 glomeruli.…”

Renal biopsy: Still a landmark for the nephrologist

“…Therefore, in a kidney in which 20% of glomeruli are sclerotic, if a bioptic sample includes five glomeruli the probability to miss affected glomeruli is about 35%. This percentage falls down to 10% if the bioptic sample includes ten glomeruli and to 1% if it includes twenty glomeruli [16,17] . Therefore, the minimum number of glomeruli required to define an adequate bioptic sample is ten, and usually, to get this target at least two different cores are taken which are divided for light microscopy (LM) (placed in formalin or another fixative), immunofluorescence (IF) (placed in transport solution saline solution and quickly freezed), and electron micro scopy (EM) (fixed in 2%-3% glutaraldehyde or 1%-4% paraformaldehyde) [18] .…”