Rapid antigen tests (RATs) have become a mainstay in the microbiology laboratory. Their use is widely accepted, and they are cost-effective alternatives to traditional cultural methods. Many clinicians don’t think twice about using RATs, especially for bloodstream isolates, but sometimes questions arise regarding their performance. Tests done using rapid antigen tests are usually done in the lab. This is because the results are best evaluated when they are fresh and new. It is important to note that rapid antigen tests are not the same as the ELISA test, which is usually done in a lab. Rapid antigen test in Australia can be conducted in the lab and at home. Antigen tests are the first step in diagnosing and treating many chronic illnesses. They are very common in immunology, allergy, internal medicine, and research laboratories. These tests can be used to identify infections, allergies, cancers, autoimmune diseases, and even pregnancy.
The most important factors to consider when choosing an antigen test are:
- Sensitivity – is it able to detect your antigen?
“Sensitivity” measures how well the test works at detecting a certain substance (antigen) at various dilutions. A sensitive test is able to detect lower concentrations of an antigen than a less sensitive one; at higher concentrations, however, the sensitivity is not as important because it will detect it all. Antigen detection limits are often expressed as a range (for example, between 0 and 100 units per milliliter). The lower limit of detection for your antigen should be within this range for your test to be useful. Another way of looking at sensitivity is to measure whether a good amount of serum/plasma/blood was added to the sample (a higher amount of serum/plasma/blood typically provides more target cells for your antigen).
- Sample type
Sample type refers to the sample volume required to run the test: serum, plasma, or buffy coat. The vast majority of RATs require an EDTA-K3 treated plasma (or serum) sample for testing. However, there are cases where serum or buffy coat samples can be used instead of plasma. For example, if you’re using a solid-phase ELISA format (as is most commonly done), you can’t use a whole blood sample because the antibodies won’t bind well to the solid phase. So if whole blood is used for testing on a solid phase ELISA format RAT, it should be done on a serum sample (or a mix of serum and plasma).
- Type of results desired
Rapid test results vary by type of result generated and available turnaround times. For example, an immunoassay-based test may provide qualitative positive or negative results. In contrast, an enzyme immunoassay (EIA) could provide quantitative results, such as amounts per volume (ng/mL). A competitive binding assay (CBA) could provide both qualitative and quantitative results based on competition between the analyte and a labeled detector antibody. In addition to differing results, some tests may be intended for use with patient specimens and others with environmental samples.