AgNOR cut-point to distinguish mild and moderate epithelial dysplasia

Distinguishing mild and moderate epithelial dysplasia is difficult and controversial. We demonstrated earlier that silver-stainable nucleolar organizer region (AgNOR) is a simple, inexpensive and quantifiable method which can standardize this distinction reliably.

To establish a cut-point mean AgNOR count for epithelial dysplasia validated by bootstrapping.

One hundred oral leukoplakia biopsies at Dr R. Ahmed Dental College, Kolkata, India, examined for epithelial dysplasia using standard method (gold standard) were assessed for their mean AgNOR counts. A cut-point was selected employing receiver operating characteristic (ROC) curve. This estimate was stabilized by 10 000 resamples (with replacement) using parametric and non-parametric bootstrap, a Monte Carlo statistical method, corrected for bias to estimate standard errors (SE) of cut-point.

Area under the curve (AUC) was 74%; non-parametric method suggested mean AgNOR cut-point = 2.42 AgNORs/nucleus; parametric method suggested cut-point = 2.57. The cut-point 95% confidence intervals (CIs) (bias corrected and accelerated) from parametric method (2.31; 2.66) was lower than non-parametric (2.43; 2.82).

Applying a conservative paradigm, taking the lowest of all bootstrap 95% CIs, we suggest that mean AgNOR count of 2.3 be used as a cut-point for distinguishing between mild and moderate dysplasia. This strategy will provide an inexpensive, meaningful, definitive, reproducible and consistent diagnostic test for epithelial dysplasia.