Lateral flow assays are the most widespread diagnostics tool used outside the laboratory. The technology behind this ubiquitous tool is an immunoassay that operates on a paper strip, enabling the detection and quantification of analytes in complex mixtures.

Typically, this rapid test consists of overlapping membranes: a sample pad where the sample is applied; a reagent pad containing antibodies targeting the specific analyte; a reaction or detection zone where anti–target analyte antibodies are displayed in a line, acting as a capture zone; and a waste-reservoir absorbent pad that guides the sample by capillary action.

The assays work when a liquid sample containing the analyte of interest is applied to one end of the strip and moves through it by capillary force. The antibodies attached to the pad interact with the analyte when it pasess by. These antibodies are typically conjugated to colored particles (generally latex microspheres or colloidal gold). The target analyte bonded to the conjugated antibody migrates along the strip until reaching the reaction zone, where anti–target analyte antibodies react with the analyte bound to the conjugated antibody. This results in a colored line. A second colored line is often present as a control, indicating the proper liquid flow through the strip.

Some of the advantages of this method include its long shelf life, lack of refrigeration requirements, ease of use, inexpensive production cost, and the fact that it is widely accepted by users and well-known by regulatory authorities. The latter constitutes an essential part of its success, as typically new diagnostic techniques require hundreds of millions of dollars in investment and a relatively long period of time to obtain regulatory approval.

As lateral flow assays can easily be transported to remote sites and ambulatory care settings, they are a practical alternative for point-of-care diagnostics. This branch of the diagnostics market is growing at a rapid rate, as it allows detection on site of a disease outbreak or food poisoning, among many other applications. As strips are extremely versatile and analytes can be anything from blood proteins to mycotoxins or viral particles, this technology can be applied to almost any industry. The most common markets are clinical settings, agricultural, food, biodefense, environmental and veterinary.

With initiatives focusing on precision medicine, the US is the largest market. Demand for lateral flow assays will continue to grow at a fast pace in this region. Large investments in hospitals and health care in Europe and North America will drive the sales growth of lateral flow testing in those markets, while food safety initiatives in Asia will also help boost market size.

Leading Vendors:

• Abbott
• Roche
• Becton, Dickinson

Largest Markets:

• Clinical testing
• Agriculture and Food
• Environmental

Assay Cost:

• $1–$100