In these expressions, TP is the number of predicted epitopic amino acids proven to be the true epitopic amino acids. FP is the number of predicted epitopic amino acids proven not to be the true epitopic amino acids. TN is the predicted non-epitopic amino acids proven not to be the true epitopic amino acids. FN is the number of predicted non-epitopic amino acids proven to be the true epitopic amino acids. We use PE to denote the number of all predicted epitopic amino acids (the sum of TP and FP).