A cassette is disclosed that permits, with an instrument, quantitative analysis to be performed at the moment of sample testing without additional steps to the end user. The cassette includes a calibration strip and a sample strip. The calibration strip contains known quantities of analyte, from which a calibration curve can be created and applied to the analysis of the sample strip. The disclosed cassette can utilize light transmission or light reflectance techniques. The cassette may include a separate wash port for rapid washing of a high background sample. The disclosed cassette may perform diagnostic tests for humans, animals, environmental sample, and/or food samples. In some cases, the disclosed devices and techniques may be used to monitor efficacy of drug therapy and patient compliance with respect to physician-prescribed medication in a point of care setting.