Fluorescent immunoassays are simply a different type of immunoassay. The key variable is the biochemical technique used to detect the binding of the “detection” antibody and the analyte molecule. The advantages of a fluorescent detection system have been known for many years. These include higher sensitivity detection of the analyte, simplified reagents, and simpler assay designs.
Several advances have occurred in recent years that have enabled the implementation of a fluorescence-based immunoassay system at the point of care. A modern fluorescence-based immunoassay uses as a detection reagent a fluorescent compound that absorbs light or energy (excitation energy) at a specific wavelength and then emits light or energy at a different wavelength. The difference between the wavelength of the excitation light and the emission light is called the Stokes shift.
The greater the change or difference in wavelength, the less interference when the excitation light is detected as part of the emission light. Recently there have been a series of technical improvements that have allowed the implementation of a highly sensitive immunoassay system. These include the availability of low-cost, narrow-wavelength light sources, newer, stable fluorophores that have very wide Stokes changes, stable solid-state light detectors, and microprocessors to process and analyze the data from each test.
When a fluorescent detection system is connected to a lateral flow assay and combined with a powerful yet low-cost analyzer such as the Quidel Sofia or Sofia 2, the result is improved assay performance, the opportunity for independent testing in conjunction with eliminating misinterpretations often associated with sight reading point-of-care trials.