Rapid immunoassays are a subset of immunoassay techniques designed for fast and on-site detection of specific molecules, often within minutes.
They are commonly used in clinical diagnostics, point-of-care testing, and various other applications. The working mechanism of a rapid immunoassay is generally straightforward and follows these steps:
- Sample Application: A small amount of the biological sample, such as blood, urine, or saliva, is applied to the test device, often using a sample pad or well.
- Lateral Flow: Rapid immunoassays typically utilize a lateral flow format. In this format, the sample flows across a membrane, carrying the target molecule if it is present.
- Capture Antibody: Specific antibodies or antigens, immobilized on the test strip, capture the target molecule if it’s present in the sample.
- Detection: A secondary antibody, conjugated to a visible marker (e.g., colloidal gold particles or fluorescent tags), binds to the captured target molecule, forming a visible line or signal on the test strip.
- Signal Visualization: The appearance of one or more lines or signals in specific regions of the test strip indicates a positive result. The absence of these lines indicates a negative result.
Two common uses of rapid immunoassays are:
- Pregnancy Tests: Rapid immunoassays are widely used for home pregnancy testing and in clinical settings to detect the presence of human chorionic gonadotropin (hCG) in urine. A positive result indicates pregnancy.
- Infectious Disease Diagnosis: Rapid tests are used to diagnose infectious diseases like HIV, hepatitis, and COVID-19. They offer quick results, making them valuable in controlling the spread of infectious diseases and for on-the-spot patient care decisions.
Rapid immunoassays are appreciated for their simplicity, speed, and suitability for point-of-care applications, enabling healthcare professionals and individuals to obtain fast results without the need for specialized laboratory equipment.