This disclosure relates generally to the field of immunological-based diagnostic assays including an assay to measure cell-mediated immunoresponsiveness. The present disclosure teaches diagnosis of a subject's exposure to an antigen based on cell-mediated immunoresponsiveness with enhanced sensitivity. Lymphocytes from a subject are contacted with at least a first set of peptides comprising at least one peptide of from 7 to 14 amino acid residues in length and a second set comprising at least one peptide of 16 amino acid residues or greater and the presence or elevation of an immune molecule is detected. The assay contemplated herein is capable of integration into standard pathology architecture to provide a diagnostic reporting system and to facilitate point of care clinical management.