Paper-based devices referred to as lateral flow tests are used in detecting the presence or absence of an analyte targeted in a liquid matrix such as pathogens, contamination in a water supply system, animal feeds, foodstuffs or even biomarkers in animals or humans. This test method usually replaces the costly and specialized equipment when doing diagnostic tests on medical issues either for point of care testing, home testing or even laboratory use. There are so many commonly used lateral flow tests including the home pregnancy test. There are various capillary beds including micro-structured polymer, pieces of porous paper or even sintered polymer that help in transporting fluids simultaneously.
The two most common types of lateral flow test include the sandwich assays and the competitive assays. Both works differently where a positive test in sandwich assays will be known when a coloured line appears at the test line position while in competitive assays, a positive test will be indicated when a positive line does not appear at the test line position. In sandwich assays, a second line usually appears on the test line position and usually contains the antibodies that have picked the latex or the gold confirming a correct operation of the test. The sample used in the lateral test flow usually moves through the test tube into the conjugate pad, to the nitrocellulose membrane till it gets to the absorbent pad. Accurate and efficient results can be obtained by ensuring that the label development enhances easy interaction with the antigens and antibodies in the sample.
Absorption of the sample usually takes place at the sample pad which may have filters to ensure there is controlled and accurate flow of the specific sample such as urine. If the targeted analyte are present in the sample as it moves through the conjugate pad, they will combine with the conjugated labels and antibodies and continue moving along the test device. At the nitrocellulose membrane, the binding reagents will bind at the test line to the target. Depending on the content of the analytes, a coloured line will appear showing a positive result. In order to know of the exact quantity of the analytes in the sample, a reader in the lateral flow test can be used. The absorbent pad usually absorbs the sample which is in excess.
Human and animal contamination can be prevented once a lateral flow reader is used as it helps determine the number of mycotoxins present in food and other agricultural produce. These tests are quite speedy and simple way to obtain the test results within just a few minutes. Also , a little sample is used is needed to carry out the test and does not require preparation of reagents.