assay - a quantitative or qualitative test of a substance (especially an ore or a drug) to determine its components; frequently used to test for the presence or concentration of infectious agents or antibodies etc.

immunoassay, immunochemical assay - identification of a substance (especially a protein) by its action as an antigen; "PSA in the blood can be measured with an immunochemical assay"

pregnancy test - a physiological test to determine whether a person is pregnant

assay - analyze (chemical substances)