Understanding the different test in Covid-19
There are several tests used to confirm the diagnosis of covid-19 infection. I will be presenting the commonly used tests and as discussed in the recent “Masterclass in Pediatrics 3 Post-Graduate Course of the Department of Pediatrics of the University of the East Ramon Magsaysay.”
1. Rapid Polymerase Chain Reaction (RT-PCR)
– detects the viral genome
– a swab is taken to take a sample of the virus from the back of the nose or throat, where the virus usually stays
– has a very high specificity and moderately high sensitivity
– best used to diagnose symptomatic or asymptomatic phases of the illness
– RT PCR test makes it possible to detect just one virus particle through the amplification process
– There is a very high specificity and moderately high sensitivity
2. Antibody Test
– Serology or Antibody test uses blood for testing
– The Phil Covid -19 Living Recommendations is against using rapid antibody tests to determine Covid-19 seroprevalence among adults( very low quality of evidence)
3. Antigen Test
– antigen tests are immunoassays that detect the presence of a specific viral antigen, which implies current viral infection
– samples are collected using nasal or nasopharyngeal swab or even saliva
– the positive antigen test is reliable only when the patient is symptomatic and a negative test is reliable only if the patient is asymptomatic and has no known history of exposure
– otherwise in other situations a follow up RT-PCR is needed
– this test can be used as a quick way to identify infected patients in triage and isolation can be done immediately- in general, the use of rapid antigen test is recommended under these conditions in patients suspected of Covid-19 infection:
a. Symptomatic
b. Early phase less than or equal 7 days from onset of symptoms and
c. Specific brands that demonstrated sensitivity >80%
Source:
A masterclass in pediatrics 3 book
Post-Graduate Course
Covid-19 edition
UERMMMCI
Department of Pediatrics, 2021