Coronavirus disease 2019, or “COVID-19,” is an infection caused by a specific virus called SARS-CoV-2. The virus first appeared in late 2019 in the city of Wuhan, China. But it has spread quickly since then, and has been declared a global pandemic by WHO since March 2020.
NAAT (nucleic acid amplification test)
- Primary use: Diagnose active/current infection
- Specimen Type: Nasopharyngeal swab or nasal swab are most common
- How it works: It looks for the genetic material of the coronavirus. The test uses a technology called PCR (polymerase chain reaction), which amplifies the viral genetic material if it is present.
- Accuracy: High sensitivity and specificity, i.e. the most reliable test. It does depend on how the specimen was collected and handled false negative rate is typically < 5% but can be up-to 40% when accounted for other factors. A single positive test generally confirms the diagnosis. If initial testing is negative and clinical suspicion remains, performing a second test can enhance diagnostic yield.
- How quick is it: Samples are generally sent to reference/central labs for analysis. Typically takes 1-3 days. Abbott ID Now is a rapid NAAT which can yield results in 13 minutes. This test will be available at our Covid-19 testing clinic in Buffalo Grove by early to mid October.
Serology
- Primary use: Diagnose past/previous infection and perhaps immunity
- Specimen Type: Blood
- How it works: It looks for antibodies to the coronavirus. Our body produces antibodies in response to the infection from coronavirus. These antibodies generally arise after days to weeks after infection
- Accuracy: Sensitivity and specificity are highly variable. Detectable antibodies generally take several days to weeks to develop; IgG usually develops by 14 days after onset of symptoms. Cross-reactivity with other coronaviruses has been reported. There are about 120 tests in the market and most have not obtained FDA EUA.
- How quick is it: Samples are generally sent to reference/central labs for analysis. Typically takes 1-3 days. There are too many “RAPID” antibody tests which can yield results in a few minutes, but they are quite unreliable.
Antigen test
- Primary use: Diagnose current infection
- Specimen Type: Nasopharyngeal swab or nasal swab
- How it works: It identifies virus in nose and throat secretions by looking for proteins from the virus (as opposed to the diagnostic test/NAAT, which looks for genetic material)
- Accuracy:Antigen tests are generally less sensitive than nucleic acid tests. They can be used for mass screening. The most known test is Sofia Quidel.
- How quick is it: These tests provide quick/rapid results in < 1 hour. Can be done at the physician’s office.
At our Covid-19 testing site in Palatine, we offer gold standard NAAT/PCR test as well as serology test through reference labs (Ten Healthcare and Quest). Abbott ID NOW rapid test (best rapid test in market) will be available by early to mid october at our Covid-19 testing site serving Arlington Heights and Buffalo Grove.
