The Accudoctor Dog Pregnancy Test (RLN) Test operates using a sandwich lateral flow immunochromatographic assay. The cassette contains a testing window with two zones: a T (test) zone and a C (control) zone, which are initially invisible. Once the sample is applied to the sample well, the liquid flows laterally along the test strip. If the sample contains sufficient levels of dog relaxin, a visible T line will appear in the test zone. The C line will always appear after the sample is applied, confirming the validity of the test. This method ensures accurate detection of canine relaxin in the sample.