Devices which are paper-based used to detect 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 are referred to as lateral flow test. The tests can be used in various medical diagnostic tests such as for the point of care testing, home testing or even laboratory use which replaces costly and specialized equipment. One of the commonly used lateral flow tests is the home pregnancy test. The micro-structured polymer, pieces of porous paper or even sintered polymer are found in the capillary beds of the test devices and help in transporting fluids simultaneously.
The two most common types of lateral flow test include the sandwich assays and the competitive assays. In sandwich assays, a positive test 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. When a second line appears at the test line in the sandwich assays it usually contains the antibodies that have picked the latex or the gold confirming a correct operation of the test. A sample moves through the test tube into the conjugate pad, to the nitrocellulose membrane till it gets to the absorbent pad in the lateral flow test. To ensure accuracy and efficiency in the results obtained, the labels during development should be made such that they enhance interaction easily with the antigens and antibodies.
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. At the conjugate pad, the sample is present and if the targeted analyte is present, it combines with the conjugated labels and antibodies as it moves 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 get the right quantity and concentration of the present targets analytes, a reader can be incorporated on the lateral flow test. The absorbent pad usually absorbs the sample which is in excess.
A lateral flow test reader is very effective in determining better ways to screen mycotoxins in food and the agricultural producers to prevent lethal effects likely to happen from contamination. It is quite fast to carry out these test as it just takes a few minutes. There are no reagents that need to be prepared to carry these tests and also very little amount of sample is needed.