The FOB–TRF Combo Test is designed to detect the presence of human hemoglobin and transferrin in a single step. The test utilizes a combination of two monoclonal antibodies, specific to human hemoglobin and human transferrin respectively, which are pre–coated on an immunochromatographic membrane. When a specimen is applied to the test, the human hemoglobin and transferrin in the specimen react with the two monoclonal antibodies respectively and form a sandwich complex. The sandwich complex then migrates along the membrane chromatographically and is captured by anti–human hemoglobin and anti–human transferrin antibodies, respectively, which are also pre–coated on the membrane. The presence of the sandwich complex will result in a visible colored line on the test region of the membrane, indicating a positive result.