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CMAAO Coronavirus Facts and Myth Buster: SARS-CoV-2 serologic testing

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Dr KK Aggarwal    20 September 2020

With input from Dr Monica Vasudev

1086:   New guidelines from IDSA on use of SARS-CoV-2 serologic testing in a variety of settings

DG Alerts: The Infectious Diseases Society of America (IDSA) has published evidence-based recommendations for the optimal use of COVID-19 serologic tests. The guideline is published in Clinical Infectious Diseases.

The guideline panel agreed on 8 diagnostic recommendations:

  1. The panel suggests against using serologic testing for the diagnosis of COVID-19 infection during the first 2 weeks (14 days) following symptom onset (conditional recommendation, very low certainty of evidence).
  2. When COVID-19 infection requires lab confirmation, the panel suggests testing for COVID-19 IgG or total antibody 3 to 4 weeks following symptom onsetto detect evidence of past infection (conditional recommendation, very low certainty of evidence). When serology is being considered as an addition to nucleic acid amplification tests for diagnosis, testing 3 to 4 weeks  after symptom onset maximizes the sensitivity and specificity to detect past infection. Serosurveillance studies must use assays that have high specificity, particularly when the prevalence of SARS-CoV-2 in the community is expected to be low (≤1%).
  3. No recommendation was made, either for, or against using IgM antibodies to detect evidence of past COVID-19 infection (conditional recommendation, very low certainty of evidence).
  4. The panel suggests against using IgA antibodies to detect evidence of past COVID-19 infection (conditional recommendation, very low certainty of evidence).
  5. The panel advises against the use of IgM or IgG antibody combination tests to detect evidence of past COVID-19 infection (conditional recommendation, very low certainty of evidence). IgM or IgG combination tests are the tests where detecting either antibody class is used to define a positive result.
  6. The panel suggests using IgG antibody to detect evidence of COVID-19 infection in symptomatic patients with a high clinical suspicion and repeatedly negative NAAT testing (weak recommendation, very low certainty of evidence). When serology is considered as an add-on to NAAT for diagnosis, testing 3 to 4 weeks after symptom onset tends to maximize the sensitivity and specificity of detecting past infection.
  7. Among pediatric patients with multisystem inflammatory syndrome, the panel suggests using both IgG antibody and NAAT for providing the evidence of current or past COVID-19 infection (strong recommendation, very low certainty of evidence).
  8. No recommendation was made for or against the use of capillary versus venous blood for serologic testing to detect SARS-CoV-2 antibodies (knowledge gap).

Serologic tests must not be used to ascertain immunity or risk of re-infection. Anti-SARS-CoV-2 antibody detection cannot guide the decisions to discontinue physical distancing or decrease the use of personal protective equipment.

[SOURCE: Clinical Infectious Diseases]

 

Dr KK Aggarwal

President CMAAO, HCFI and Past National President IMA

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