Our calculated optimal FSH threshold for classifying a CCS as azoospermic is 10.4 UI/L, where optimal means providing the best tradeoff between sensitivity (i.e. minimized prediction of non-zero sperm concentration for CCS who are in reality azoospermic) and specificity (i.e. minimized prediction of azoospermia for CCS who in reality have non-zero sperm concentration). The gene discussed is BRD2; the disease is Azoospermia.