A diagnostic test kit that employs a lateral flow assay device and a plurality of assay reagents for detecting a test analyte within a test sample is disclosed. The assay reagents include detection probes that are capable of producing a detection signal representing the presence or quantity of the test analyte in the test sample. To further enhance detection accuracy, calibration probes are also used that are capable of producing a calibration signal representing the presence or quantity of a calibration analyte. The calibration signal may be utilized to calibrate the detection signal.