WHAT IS A LATERAL FLOW IMMUNOASSAY?
Lateral flow test strips based on the principles of immunochromatography exist for a wide array of target analytes. The fist tests were
made for the detection of human chorionic gonadotropin (hCG). Today, there are commercially available tests for ovulation
monitoring, infectious disease detection, drugs of abuse analysis, and measuring other analytes important to human physiology.
Products have also been introduced for testing, agricultural applications, environmental testing, and food & feed testing.
While the fist tests presented qualitative results based on the presence or absence of a signal line, test design has progressed
toward semi-quantitative and quantitative assays and the integration of hand-held readers.
A lateral flow immunoassay is described using varying terminology by different sectors and different countries. Common names
+ Lateral flow immunoassay (LFIA)
+ Lateral flow test (LFT)
+ Lateral flow device (LFD)
+ Lateral flow assay (LFA)
+ Lateral flow immunochromatographic assays
+ Rapid test
+ Test strip
+ Quick test
TYPES OF LATERAL FLOW TESTS
Lateral flow assays can be developed to be used in a dipstick format or in a cassette. Both dipsticks and cassette tests will work in a
similar way, it is just dependent on the industry, sample matrix, and the market requirement, as to which format is suitable.
The sandwich assay format is typically used for detecting relatively large analytes. If the analyte has at least two distinct binding sites
(i.e. epitopes), a “sandwich” assay can be developed where an antibody to one epitope is conjugated to the nanoparticle and an
antibody to another epitope is immobilized at the test line. The sandwich format results in a signal intensity that is proportional to the
amount of analyte present in the sample.
A competitive format is used for detecting analytes in which the analyte is too small for two antibodies to bind simultaneously, such
as vitamins and antibiotics. In