Given the diagnostic and prognostic implications when CDKN2A HD is detected in a lower grade glioma, we favored a conservative threshold p16 expression value of 5%, which optimizes both test specificity and positive predictive value for CDKN2A HD detection, over a threshold of 10% or higher, which leads to occasional overcalling of CDKN2A HD (i.e. false positives). The gene discussed is CDKN2A; the disease is central nervous system cancer.