A material which is used to establish known points of reference for an assay intended to be used for the qualitative and/or quantitative detection of multiple chemical and/or biological markers to help differentiate bacterial from viral infection in a clinical specimen. Analytes assayed may include C-reactive protein (CRP), myxovirus resistance protein 1 (MxA), tumour necrosis factor-related apoptosis-inducing ligand (TRAIL), and interferon-gamma-induced protein-10 (IP-10).