ANALYSIS FOR MEASURING PRESENCE OF SUBSTANCE TO BE ANALYZED TEST COMPOSITION AND TEST DEVICE

An analytical method and test composition for determining whether an analyte is present in a test sample at a predetermined concentration level by measuring or observing a preselected level of indicator response, e.g., color generation. A subtractive reaction is carried out on the test sample prior to the indicator reaction in order to stoichiometrically and specifically consume a predetermined amount of analyte. The resulting indicator reaction generates the preselected level of indicator response only if the analyte is present at the predetermined concentration level or greater. The subtractive reaction is enzymatically specific for the analyte in the reaction mixture and the amount of analyte consumed can be closely controlled by the amount of a regulating coreactant present at initiation. The method enables the determination of analyte without the need for standards or comparators, e.g., color charts, and therefore is self-indicating. In another embodiment, there is provided a method and test composition for improving an otherwise suboptimal assay response due to oversaturation of the response, e.g., color, generated by an indicator reaction.