IDSA publishes recommendations for SARS-CoV-2 serologic tests
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The Infectious Diseases Society of America published new guidance on the use of SARS-CoV-2 serologic tests that included eight diagnostic recommendations.
“There's been a lot of interest in developing SARS-CoV-2-specific tests that can detect antibodies directed against the SARS-CoV-2 virus,” Kimberly E. Hanson, MD, MHS, chair of the IDSA’s COVID-19 diagnostic guidelines expert panel and associate professor of internal medicine at the University of Utah School of Medicine, said during an IDSA press briefing on Thursday.
She noted the “incredible” pace that diagnostic tests have come to market and the rapid publication of research on how they perform.
“Looking at the mishmash of stuff, it’s hard to tell on the surface how these tests perform and how we should be using them in clinical practice to manage patients and make diagnoses,” Hanson said.
With this in mind, the IDSA expert panel reviewed more than 9,400 existent papers on SARS-CoV-2 antibodies and ultimately included 47 in the evidence base for the recommendations.
“Even though it was only 47 papers, the data [were] really complicated and we saw many variables that probably [affected] the results of the test,” Hanson said, noting that the timing of antibody testing is a key component.
Eight recommendations
Following their review, the IDSA panel compiled the following guidelines for antibody testing:
Recommendation 1. Serologic testing to diagnose SARS-CoV-2 infection should not be performed during the first 14 days following symptom onset. (Conditional recommendation, very low certainty of evidence.)
Recommendation 2. When SARS-CoV-2 infection requires laboratory confirmation for clinical or epidemiological purposes, testing for SARS-CoV-2 immunoglobulin G or total antibody should be done 3 to 4 weeks after symptom onset to detect evidence of past SARS-CoV-2 infection. (Conditional recommendation, very low certainty of evidence.)
Recommendation 3. The IDSA panel makes no recommendation either for or against using immunoglobulin M antibodies to detect evidence of past SARS-CoV-2 infection. (Conditional recommendation, very low certainty of evidence.)
Recommendation 4. Immunoglobulin A antibodies should not be used to detect evidence of past SARS-CoV-2 infection. (Conditional recommendation, very low certainty of evidence.)
Recommendation 5. IgM or IgG antibody combination tests should not be used to detect evidence of past SARS-CoV-2 infection. (Conditional recommendation, very low certainty of evidence.)
Recommendation 6. IgG antibody should be used to provide evidence of COVID-19 infection in symptomatic patients with a high clinical suspicion and repeatedly negative nucleic acid amplification tests (NAAT). (Weak recommendation, very low certainty of evidence.)
Recommendation 7. In pediatric patients with multisystem inflammatory syndrome, both IgG antibody and NAAT should be used to provide evidence of current or past COVID-19 infection. (Strong recommendation, very low certainty of evidence.)
Recommendation 8. The IDSA panel makes no recommendation for or against using capillary vs. venous blood for serologic testing to detect SARS-CoV-2 antibodies. (Knowledge gap.)
Are SARS-CoV-2 antibodies protective?
Angela M. Caliendo, MD, PhD, an IDSA board member and member of the diagnostic guideline panel, said the primary use of antibody tests should be for surveillance purposes.
“By detecting antibodies, it gives us an idea of at any given time point, how many people in the population are affected, and then you can test over time and see changes in the prevalence of the antibody response in a population,” Caliedno said, adding that having a highly specific test is important for this type of surveillance.
“If you're going to do surveillance testing, and you're going to give the individual patient the result, they could be misled to think that they have had SARS-CoV-2 infection and that may lead them to believe that they're safe or protected from getting infected again, when, in fact, the reality is that they may never have been infected or even if they were infected, we don't know for sure that they're going to be protected.”
Speculation about whether SARS-CoV-2 antibodies will protect a patient from a second infection has been ongoing. One newly published study about a SARS-CoV-2 outbreak on a fishing vessel suggested they do.
According to the paper published on medRxiv, a preprint server, 104 of the 122 crewmembers of the vessel were infected after it left Seattle — an attack rate of 85.2%. None of the three crewmembers who tested positive for pre-existing neutralizing antibodies prior to departure showed symptoms or evidence of infection, demonstrating that “the presence of neutralizing antibodies from prior infection was significantly associated with protection against reinfection,” the authors wrote.
References:
- Addetia A, et al. medRxiv. 2020;doi:10.1101/2020.08.13.20173161.
- IDSA. Infectious Diseases Society of America Guidelines on the diagnosis of COVID-19: Serologic testing. https://www.idsociety.org/practice-guideline/covid-19-guideline-serology/. Accessed on Aug. 20, 2020.
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