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. However, it takes at least a day to get the results, and it can sometimes take a week or more. Note that these PCR tests, which require assay in a lab, are quite expensive -- typically costing over $100.
The 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 diagnosis.
The antigen test diagnoses the disease like PCR, and it provides results quickly like antibody testing, but it is not as sensitive as PCR. Thus, there can be false negatives. However, it has very high specificity. If you test positive, you are virtually certain to have COVID-19. Therefore, it is often the best choice for screening applications.
Narratek markets the Bluestone Safe Saliva test, analyzed on RT-PCR, and the CareStart Rapid Antigen Test, which outputs results in less than 15 minutes. See below for information about each of these FDA EUA tests.
Narratek offers the Bluestone Safe(TM) Saliva Test. It meets all the key requirements for a test that should be universally used for COVID-19 diagnosis: easy, palatable, safe to administer, highly accurate, and fast results reporting. It has been in successful use for many months during the pandemic, and the support system is impressively elegant. Of particular note, there is no need for a PPE-garbed medical tech; people just spit in a tube that has a barcode on it. They enter that number into the Health Portal, to link to their electronic record. The tubes are overnighted to the lab, and the results will be available by the end of the next day. It just doesn't get any easier than that.
Evidence on the Accuracy of Saliva Testing
Here are a couple of excerpts from this article in the LA Times:
"The saliva tests did a better job of detecting the virus formally known as SARS-CoV-2, the researchers found. In the first five days after diagnosis, 81% of the saliva tests came back positive, compared with 71% of the nasopharyngeal tests. A similar gap remained through the 10 day after diagnosis. In addition, the researchers detected more copies of the virus’ genetic material in patients’ saliva than in the samples taken from the back of their nasal cavities."
"To see how the tests stacked up among people with asymptomatic infections, the researchers recruited 495 healthcare workers with no signs of COVID-19 and gave them the saliva test. Thirteen of the tests came back positive. Among those 13 people, nine had given themselves nasal swabs on the same day, and only two of those tests came back positive. However, all 13 of the saliva tests were later confirmed by additional nasopharyngeal tests. The results were reported Friday in the New England Journal of Medicine."
The early data seem to show that, for early diagnosis, saliva testing might actually be more accurate than nasopharyngeal testing.
For further information about the Bluestone Saliva Test for COVID-19, email firstname.lastname@example.org.
CareStart Rapid Antigen Test
The CareStart Rapid Antigen test is one of only two antigen tests that has received FDA EUA and also does not require an instrument to analyze the specimen. It is self contained on a strip, providing results in less than 15 minutes. With a sensitivity around 88% and specificity close to 100%, it is a cost-effective approach for screening applications -- such as the safe operation of schools and businesses.