A reagent test paddle includes a contamination detection medium, a reference color bar, at least one chemical test medium, and a unique identifier. The contamination detection medium includes a reagent that changes color in the presence or when exposed to a hostile or inhospitable environment. Each chemical test medium includes a regent that is responsive to a respective analyte in a biological sample. The reference color bar includes reference color samples of different colors. The unique identifier, like a serial number, identifies the particular paddle and its chemical test medium so it can be uniquely and anonymously associated with a user. A method includes capturing and interpreting digital images of a biologically unexposed and subsequently exposed reagent test paddle at various delay times within an automatically calibrated environment; locating the paddle in a plurality of digital images, extracting the reference color bar and locating the contamination detection medium and chemical test medium in each digital image. Color changes of the chemical test medium and contamination medium are detected at various delay times after sample exposure. To determine validity of test results, the method further compares the detected colors of the contamination detection medium with predetermined colors expected for no contamination and contamination.