There are three primary types of tests being deployed during this pandemic: RT-PCR, rapid antibody, and rapid antigen.
PCR is a molecular or nucleic acid test, which determines if SARS-CoV-2, the coronavirus that causes COVID-19, is present in the sample. The sample is typically obtained via deep nasopharyngeal swab. However, doing less invasive sampling -- anterior nasal swab or saliva -- is gaining traction. PCR testing is the gold standard. It takes at least a day to get the results, sometimes much longer. Note that these PCR tests, which require assay in a lab, are quite expensive -- typically costing over $100.
The rapid antibody test looks for antibodies to the coronavirus in a fingerstick of blood. Since these antibodies (IgM and IgG) do not appear in the blood until perhaps 1-2 weeks following the onset of symptoms, this test is only useful to know if some has had the disease and might now have some immunity. It is of virtually no use for diagnosing current illness.
The rapid antigen test will diagnose the disease as with PCR, and it provides results very quickly like antibody testing. But antigen testing is typically not as sensitive as PCR, since it does not amplify the viral DNA. Thus, there can be false negatives. However, these tests do have very high specificity. If you test positive, you are virtually certain to have COVID-19. Therefore, they are often used for screening applications. The Siemens Rapid Antigen Test, marketed by Narratek, has uniquely high sensitivity, at 96.72%, which means that there are very few false negatives. Specificity is 99.22% (hardly any false positives). With an overall accuracy of 98.74%, it is almost as accurate as the PCR tests. Results are available within 15 minutes, and the price is a tiny fraction of the cost of PCR testing. The delivered price is $13 per test for the minimum order quantity of 400 tests. There are discounts for larger orders.
Narratek provides what we believe are the two best tests in the market, with very high accuracy and relatively low cost. One is a rapid antigen test; the other is a saliva PCR test. See below.