Immunochromatography or lateral flow immunoassay (LFIA) is a fast, easy, and popular technique for the identification of target molecules in various matrices including blood, urine, and saliva. This technique has proved to be very useful in fields such as medicine, food safety, and environmental health since it is fast, easy to perform, and cheap. In the following article, we will discuss the workings of immunochromatography, its uses, and the pros and cons of this technique.
Immunochromatography is a type of diagnosis whereby antibodies and antigens are used to determine the presence of certain molecules in a given sample. It is a paper-based system where the samples move along the paper strip by the use of capillary action. When the sample interacts with specific antibodies on the strip, a reaction takes place, especially developing a visible line. This technique is applied in home pregnancy tests, rapid COVID-19 tests, and many other point-of-care diagnoses.
The immunochromatographic process involves several key components: The immunochromatographic process involves several key components:
The sample pad is the pad that is used to place the liquid sample. This pad assists in the regulation of the rate of flow of the sample and may also contain chemicals that assist in the preparation of the sample for analysis. In some tests, the sample may be required to be mixed with a buffer solution to achieve the best results for the test.
The conjugate pad lateral flow has antibodies that have been attached to colored or fluorescent particles. These antibodies are selective for the target analyte. When the sample passes through the conjugate pad, these target molecules attach themselves to these labeled antibodies to form a complex.
The nitrocellulose membrane is the most important component of the immunochromatographic strip. This has the test line and the control line. The test line has captured antibodies that are specific to the target analyte while the control line has antibodies that react with the labeled antibody. When the sample is traveling through the membrane, the target analyte reacts with the antibodies at the test line and forms a visible signal. The control line enables the assessment of the test through the interaction with the labeled antibodies that did not combine with the target analyte.
The absorbent pad located at the end of the strip is useful in drawing out excess flow through the membrane to maintain a constant flow. This aids in giving the strip a termination point thus helping to complete the process.
Immunochromatography is applied in various fields, including biological, chemical, and medical ones. Due to its capacity to deliver quick and accurate results in the post environments, it has become an essential tool in many sectors.
Immunochromatography has found its application in many fields, but perhaps the most famous one is in the medical field as a diagnostic tool. One of the most widespread examples of home diagnostic tools is home pregnancy tests that find human chorionic gonadotropin (hCG) in urine. Immunochromatography is also applied in the diagnosis of infections such as malaria, HIV, hepatitis, and COVID 19 among others.
Immunochromatography is used in food safety to identify pathogens, toxins, and allergens that are dangerous to human health. For instance, it may be applied in checking for E. coli or salmonella in foods or peanuts or gluten in foods.
In environmental analysis, immunochromatography is applied for the identification of pollutants like pesticides, heavy metals, and toxins in water and soil. This application is very important in preventing environmental risk and guaranteeing the absence of risky chemicals in drinkable water and foods.
The most common application of immunochromatography is in drug testing of which urine testing for illicit substances is very popular. It can give quick results right at the scene, and it can be used at the scene of the crime or when testing employees before hiring them.
Immunochromatography is such a popular diagnostic technique for the following reasons;
However, like with any other diagnostic technique, immunochromatography does have certain drawbacks.
Immunochromatography, also called lateral flow immunoassay, is one of the most used diagnostic techniques in diagnostics because of its simplicity, speed, and cost. This method is employed in medicine, food hygiene, environmental diagnostics, and drug analysis among others, and is characterized by fast and accurate detection at the POC. While it may not be as sensitive and specific as traditional methods performed in a laboratory, constant improvement has been made such as nanoparticle tests and integration of the test with smartphones. Immunochromatography will be a valuable diagnostic technique as technology advances, especially where rapid and field diagnosis is desirable.
Immunochromatography and ELISA are two types of immunoassay that involve the use of antibodies to identify specific compounds. Nonetheless, immunochromatography is more efficient, less complicated, and does not require any special equipment for testing making it appropriate for point-of-care testing. ELISA is more sensitive and specific and the test has to be done in a laboratory by laboratory personnel.
Immunochromatography is used for the detection of COVID-19. The COVID-19 rapid antigen tests use immunochromatography, in which the viral proteins located in the nasopharyngeal swabs or saliva are detected. These tests provide results in as little as 15 minutes making them ideal for screening and point-of-care testing.
The immunochromatographic tests’ sensitivity depends on the quality of the test, the sample used, and the target analyte. They are especially useful for initial screening but false positives can be obtained and if the concentration of the target analyte is low, then false negatives can also be obtained. Additional tests that may be conducted include PCR or ELISA which are laboratory-based tests.
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