Diagnostic testing for COVID-19

By EricAdamson

There are three COVID-19 diagnostic methods available: antigen, molecular and antibody. Each method has its own advantages and disadvantages. The nursing knowledge is essential to ensure that accurate day 2 test is used, applied, and interpreted.

Various nations and certifying organizations–including the World Health Organization (WHO), Conformite Europeenne, and the U.S. Food and Drug Administration (FDA)–have approved over 400 molecular, antigen, and serological antibody diagnostic tests for SARS-CoV-2. Nurses should consider the following factors when deciding which test to use: method of sample collection, process procedure, time required for results, test sensitivity, specificity, limitations and interpretation. There are three types of testing methods: antigen, molecular and antibody.

Molecular testing

To diagnose COVID-19 active or acute COVID-19 virus infection, a variety of molecular tests can detect RNA from SARS-CoV-2 viruses. Examples include the nucleic acid amplification test (NAAT), real-time reverse transcription-polymerase chain reaction (RT-PCR), and loop-mediated isothermal amplification (LAMP). The sample collection routes include the nasopharyngeal and deep nasal, anterior, nares, oropharyngeal. Molecular test results are available in 1-3 to 4 hours depending on laboratory capabilities. The average time is between 1 and 2 days.

There are many advantages. RT-PCR is the Gold Standard for diagnosing SARS/CoV-2 virus. Because they are highly sensitive and specific, Molecular tests can also be used to confirm antigen testing results.

Antigen testing

Antigen tests can detect surface proteins of the SARS-CoV-2 viruses to diagnose active or acute infections. The anterior nares and nasopharynx are used to collect specimens. Individuals with symptoms within the first five to seven days of infection should have antigen testing. A Cochrane systematic review of 22 antigen test research studies revealed that the sensitivity ranged from 0% to 94%. The average sensitivity was 56.2%. This is why a confirming RTPCR test is recommended.

There are many advantages. Point-of-care tests take 15 to 30 minutes to produce results, while antigen tests can provide faster results than molecular tests. Antigen tests are also less expensive than RT-PCR tests, and do not require specialized laboratory techniques.

Antibody testing

To detect an infection in the past, antibody testing requires either a blood sample from a vein or finger prick. These tests can be performed using immunoassay or lateral flow tests such as the ELISA and CIA (chemiluminescent immuneassay). Antibody testing can be used to determine whether there are immunoglobulin M or immunoglobulin G antibodies that were produced in response to infection.

There are many advantages. Asymptomatic individuals can be identified by antibody testing. This information can be used to guide transmission control measures, such as isolation, quarantine, social distancing and closure of schools, worship places, and businesses.