Check4® Pregnancy-M is a rapid qualitative assay for the detection of human chorionic gonadotropin in serum and urine. The method employs a combination of monoclonal-dye conjugate and polyclonal-solid phase antibodies to selectively identify hCG in the test samples with a high degree of sensitivity. Within 10 minutes, levels of hCG as low as 25 mIU/mL can be detected. As the test sample flows through the absorbent device, the labelled antibody-dye conjugate binds to the hCG forming an antibody-antigen complex. This complex binds to the anti-hCG antibody in the test zone (T) and produces a pink colour band when hCG concentration is higher than 25 mIU/mL. In the absence of hCG, there is no line in the test zone (T). The reaction mixture continues flowing through the absorbent device past the test zone and control zone. Unbound conjugate binds to the reagents in the control zone (C), producing a pink colour band, demonstrating that the reagents are functioning correctly.