A lateral flow assay, also called a lateral flow immunochromatographic assay, is a simple type of immunoassay used to detect the presence or absence of target analytes in a sample without using sophisticated laboratory equipment. It consists of a sample pad, conjugate pad, nitrocellulose membrane, and wicking pad arranged in a row or lateral flow configuration inside a plastic cassette or housing.
How does a lateral flow assay work?
In a basic lateral flow assay setup, target analytes in a sample are reacted with labeled detection reagents such as antibodies, antigens or haptens coated with colored particles during sample migration. The antigen-conjugate complex is then captured by immobilized antibodies deposited in a test line. Unbound conjugate particles continue to flow and are captured in a control line. This results in the formation of visible colored lines. The intensity of the test line indicates a positive or negative result depending on whether the target analyte is present in the sample above a certain threshold concentration.
Components of a lateral flow assay strip
The key components of a typical lateral flow assay strip include a sample pad, conjugate pad, nitrocellulose membrane and wicking pad. The sample pad is responsible for receiving and filtering the liquid sample. The conjugate pad contains the detection reagents like antibodies labeled with colored particles. The nitrocellulose membrane acts as the support for the test and control lines. It is made of a porous material that allows capillary flow. The wicking pad absorbs and transports the sample along with unbound conjugate particles to complete the assay flow.
Applications of lateral flow assays
Due to their simplicity, speed and lack of requirement for complex instrumentation, lateral flow assays have found widespread applications in point-of-care testing across various fields like healthcare, food safety testing, biodefense and environmental monitoring. Some common examples include pregnancy tests, drug screening tests, malaria rapid diagnostic tests, microbiological assays for detection of foodborne pathogens and mycotoxins, and water quality tests for detection of bacterial contamination. Lateral flow assays have enabled fast and reliable testing outside centralized laboratories.
Advantages of lateral flow assays
The major advantages of lateral flow assays include ease of use with no specialized training required, rapid results within 5-30 minutes, low cost per test, stability at room temperature without any refrigeration, and portability for use in resource-limited settings. They provide a simple yes/no qualitative result without the need for expensive readers or instrumentation. The compact format also allows integration of all required reagents in a small cartridge for true point-of-care and field-based testing applications.
Limitations of lateral flow assays
While lateral flow assays offer an inexpensive solution for rapid screening, their sensitivity and specificity may be comparatively lower than laboratory based analytical techniques. The results are usually semi-quantitative rather than quantitative. Interference from sample matrix can occasionally affect test performance. Storage and transportation also need to be carefully controlled to avoid degradation of assay components during shelf-life. Standardization and validation of assays remains an area requiring ongoing quality control measures.
In conclusion, lateral flow assays have revolutionized point-of-care testing by providing a simple and rapid solution for detecting target analytes without the need for specialized equipment or technical expertise. Their widespread applications across various fields underscore their utility for screening and preliminary diagnosis in resource-limited settings near the site of sample collection. Continued research focusing on assay multiplexing, quantitative readout and standardization would help realize their full potential as reliable tools for decentralized testing.
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1. Source: Coherent Market Insights, Public sources, Desk research
2. We have leveraged AI tools to mine information and compile it
