The importance of sample size in the interpretation of the renal biopsy.

The number of abnormal glomeruli present in a renal biopsy can be viewed as a binomial distribution. Recognition of this fact permits a quantitative assessment of the effect of biopsy sample size in renal biopsy interpretation. If the percent of glomerular involvement in a biopsy is used to determine the severity of a focal glomerular lesion, a small biopsy sample size will lead to considerable misclassification of disease severity. In addition, a small biopsy sample size will make the exclusion of focal disease difficult.