Lateral Flow Tests

Lateral flow assay development is the successful production of a simple to use diagnostic test for validating the presence or absence of a wide range of pathogens, biomarkers and antibodies in a specific species. Rapid lateral flow tests are used for qualitative and quantitative analysis. Qualitative by visually indicating if a substance is present and quantitative by determining how much of that substance is present.  Lateral flow immunoassay tests are highly important and versatile within point-of-care diagnostics.

How Do Lateral Flows Work?

Components of the test flow laterally through the devices grid allowing for antigens to combine with antibodies to signal a response between the complexes. The components involved in a lateral flow assay are the sample pad, a conjugate pad, a nitrocellulose membrane, and a absorbent pad.

Subjects specimen is collected and introduced to the sample pad or device.

The sample moves onto a conjugate pad. This pad is typically coated with the desired conjugated antibody, such as colloidal gold or other fluorescent particles. If the target is present, the immobilized conjugated antibodies and labels will bind to the target forming complexes and continue to migrate along the test.

As the sample and antibody complex moves onto the antigen-coated nitrocellulose test line, interaction occurs. If the target antigen is present, a colored line will form and the density of the line depends on the quantity of that antigen present. To quantify and determine target concentration results, a rapid test can be combined with a digital reader. When there are no antibodies specific to the antigen, this results in no colored line to develop indicating a  “negative”  test.

Most tests will contain a second line, called the control line, which is coated with antibodies to pick up the excess gold conjugates particles. This results in a second colored line indicating the flow test operated correctly.

The sample will then reach an absorbent pad. This primary functio