IgM and IgG Antibody Tests for COVID-19
There are an emerging amount of IgG and IgM antibody tests for COVID-19 that are being developed and presented to clinicians. Currently, the most widely used method for diagnosing COVID-19 is the standard M PCR. This test is the most sensitive testing method and can identify the virus before symptoms are expressed. When determining which test is right for your patient, it is important to look at the epidemiology of SARS-CoV-2.
- As with other coronaviruses, it appears that after initial infection, the typical patient will see symptom onset around day five and will begin to develop IgM antibodies around eight days post infection and IgG antibodies around 14 days post infection.
- The COVID-19 Human IgM IgG Rapid Test can be used to test serum collected from patients between eight days up to 10 weeks from likely risk of COVID-19 virus exposure or post-onset of symptoms.
- If a specimen is collected prior to 8 days post-onset of symptoms or likely risk of COVID-19 virus exposure the patient should be asked to return and provide a second blood sample at least seven days after the initial blood specimen.
Confirmation of a presumptive positive result requires additional testing by CDC or by qualified laboratories designated by CDC and in consultation with Centers for Disease Control and Prevention, using the CDC-issued algorithm. Laboratory test results should always be considered in the context of clinical observations, epidemiological data, and travel history in making a final diagnosis and patient management decisions.
Pros of Human IgM IgG antibody tests:
- Results take about 15 minutes.
- Accurate: High sensitivity and specificity.
- Low cost.
- Ease of use; no need for laboratory personnel, equipment or sample transport.
- Can be easily mass produced to over 200,000 per day.
- Reliably detectable for approximately 2 (IgM) and 4 (IgG) weeks following infection.
- Useful for asymptomatic patients and for patients who may have previously been infected.
- Cons of Human IgM IgG antibody tests:
- The majority of these tests have not been reviewed by the FDA.
- Unable to diagnose at early stage of infection.
- Negative results do not rule out SARS-CoV-2 infection, particularly in those who have been in contact with the virus.
- Follow-up testing with a molecular diagnostic should be considered to rule out infection in these individuals.
- Results from antibody testing should not be used as the sole basis to diagnose or exclude SARS-CoV-2 infection or to inform infection status.
- Positive results may be due to past or present infection with non-SARS-CoV-2 coronavirus strains, such as coronavirus HKU1, NL63, OC43, or 229E or for patients who have received SARS and MERS vaccinations.
Many of these tests are available under an emergency access mechanism called an Emergency Use Authorization (EUA). The EUA is supported by a Secretary of Health and Human Service’s (HHS’s) declaration that circumstances exist to justify the use of in vitro diagnostic devices (IVDs) under EUA for the detection of COVID-19 virus and/or diagnosis of COVID-19 virus infection.
An IVD made available under an EUA has not undergone the full validation of an FDA-approved or cleared IVD. The COVID-19 Human IgM IgG testing should be performed by laboratories in the U.S. that are certified under the Clinical Laboratory Improvement Amendments of 1988 (CLIA) to perform high or moderate complexity tests, or by similarly qualified non-U.S. laboratories. When choosing a company to work with, verify that they have notified FDA that they have validated and are offering serology tests as set forth in Section IV.D of the FDA's Policy for Diagnostic Tests for Coronavirus Disease-2019 per the FDA’s policy for EUA .