Rapid Lateral Flow Assays
Lateral flow assays are a quick and convenient diagnostic test format used to confirm the presence or absence of a target analyte, such as infectious pathogens. They provide rapid results, sometimes in as little as a few minutes.
Rapid diagnostics, brings testing away from the laboratory and closer to the patient, enabling faster decision making leading to earlier diagnosis, monitoring and treatment.
Lateral flow assays may be in a dipstick format or in a housed cassette. Both dipsticks and casette tests work in a similar way.
Lateral Flow Assays
Lateral Flow Assays (LFAs) are commonly used in POCT. These simple devices can detect the presence of a target marker in a liquid sample such as blood, saliva, urine or a faecal sample extraction. They do not require specialist or costly equipment to perform the test or read the result. The tests are simple, economic and generally show results in around five to 30 minutes.
The image shows the principal of an LFA - specifically the IMMY Cryptococcal Antigen (CrAg) assay.
Typically, the LFA consists of a sample pad, a conjugate pad, a nitrocellulose strip that contains test and control line/s and a wicking pad.
The overlapping of each component enables smooth capillary flow of the sample. Once sample is applied on the adsorbent sample pad, it migrates to the conjugate release pad containing antibodies specific to the target analyte and conjugated to fluorescent or coloured particles, usually latex microspheres or colloidal gold.
The sample containing the conjugated antibody bound to the target analyte migrates along the strip into the detection zone that contains antibodies or antigens immobilised in lines. These components react with the analyte bound to the conjugated antibody. Positive test line indicates recognition of the sample analyte while the response on the control line demonstrates proper liquid flow through the strip. The intensity of the appearing lines can be assessed either by eye or using a dedicated reader. After the control line, the sample flows into the wicking pad which maintains the capillary force and the flow of the liquid.
Lateral flow assays may be in a dipstick format or housed in a cassette. Both dipsticks and casette tests work in a similar way.
Applications
Lateral flow assays are ideal for use in Point-of-Care applications and by users without professional laboratory training,
including patients themselves.
Lateral flow devices use a combination of antibodies, nitrocellulose membranes and coloured nanoparticles to produce visually interpreted results.
They can also be combined with reader technology to produce rapid qualitative or quantitative data to enhance results.
Benefits
Simple to use
Rapid results
Convenient for Point-of-Care