A method is provided for detecting or quantitating each of a plurality of substances or at least one substance and an internal reference material or control material in a test sample using at least two different luminescent labelled conjugates. Each luminescent labelled conjugate being characterized in being activated to emit light under different process conditions. The invention also provides for test kits containing at least two different luminescent labelled conjugates for detecting or quantitating presence or absence of at least two substances or at least one substance an internal reference material or control material in a test sample.