General

Lateral flow tests (Lateral Flow Immunochromatographic Assays) are simple devices intended to detect the presence or absence of a target analyte in sample. Most commonly these tests are used for medical diagnostics either for home testing, point-of-care testing or laboratory use. They can be produced in different formats: dipstick, midstream tests or cassettes. The test sample flows along a solid substrate via capillary action. After the sample is applied to the test it encounters a colored reagent which mixes with the sample and transits the substrate encountering lines or zones which have been pretreated with an antibody or antigen. Depending upon the analytes present in the sample the colored reagent can become bound at the test line or zone. Lateral Flow Tests can operate as either competitive or sandwich assays.

Sandwich assays

The sample first encounters colored particles which are labelled with antibodies raised to the target analyte. The test line will also contain antibodies to the same target, although it may bind to a different epitope on the analyte.

The test line will appear in positive samples. See here how a sandwich test works.

Competitive Assays

The sample first encounters colored particles which are labelled with the target analyte or an analogue. The test line contains antibodies to the target/its analogue. Unlabelled analyte in the sample will block the binding sites on the antibodies preventing uptake of the colored particles.

The test line will appear in negative samples. See here how a competitive test works.

The SeraQuant algorithm takes both sandwich and competitive principles into account.