A lateral flow assay, also known as a lateral flow immunochromatographic strip test, is a simple type of immunoassay used to detect the presence or absence of targeted substances in biological samples like blood or urine. It operates on a similar principle to a pregnancy test and yields visual, colorimetric results that can be read with the naked eye.

Workings

In a Lateral Flow Assay, the sample to be tested is applied to a sample pad located at one end of a strip made of absorbent material, usually nitrocellulose. The liquid sample then flows through the strip via capillary action. As the sample flows, it encounters a conjugate pad containing labeled detector molecules such as antibodies, antigens, or haptens linked to colored particles like latex beads or colloidal gold. These labeled detector molecules bind to any target analytes present in the sample.

The analyte-detector complexes are then transported further along the strip to a reaction zone containing a test line and usually a control line. The test line contains immobilized capture molecules such as antibodies specific to the target analyte. If the target analyte is present in the sample, the labeled detector molecules bind to the capture molecules at the test line, causing it to visibly change color. The control line also contains capture molecules and ensures the test has worked properly by showing whether the strip's flow functioned correctly. Results typically appear within 15-30 minutes.

Applications of Lateral Flow Assay
Due to its simplicity, speed, affordability, and ability to be performed with minimal training in non-laboratory settings, lateral flow immunoassay has found widespread use for diagnosing infections and testing for the presence of various analytes. Some common applications of lateral flow immunoassays include:

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