COVID-19: which 4 antibody tests have the highest sensitivity, specificity — and when?

  • Green DA & al.
  • J Clin Microbiol
  • 8 Jun 2020

  • curated by Liz Scherer
  • Clinical Essentials
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Takeaway

  • An IgG serology study shows overall specificity of 98.0%-99.6% and sensitivity of 88.1%-98.8% in samples collected >14 days after disease detection for 4 high-throughput serologic tests for antibodies to SARS-CoV-2: Abbott, Epitope, Euroimmun, and Ortho-Clinical.
  • Repeat molecular diagnostic testing yielding eventual positive results can be considered a true positive for SARS-CoV-2, according to a separate study published in the same journal.

Why this matters

  • Serologic testing yields the most accurate results at >14 days after symptom onset/PCR diagnosis.  
  • Molecular testing should be repeated up to 2 days after a negative result in patients whose symptoms warrant high clinical suspicion for COVID-19.

Key results

    • IgG study:
      • Overall specificity/positive predictive values by assay, assuming 5% prevalence, >14 days since symptom onset:
        • Abbott: 99.6%/92.8%.
        • Epitope: 99.6%/90.6%.
        • Euroimmun: 98.0%/71.2%.
        • Ortho-Clinical: 99.6%/92.5%. 
      • All but 1 (Abbott) hit 100% sensitivity overall among samples >14 days following symptom onset.
    • Diagnostics study:
      • Of 3432 patients, 2630 had initial negative, invalid, or indeterminate results, and 802 had initial positive results.
      • Overall test positivity: 39.9% with repeat testing vs 49.0% with single test (P<.001>
      • Of 2413 patients first testing negative, 18.6% became positive on repeat testing on subsequent days.
        • Negative predictive value: 81.3% (95% CI, 79.7%-82.8%).
      • Same-day repeat testing of patients with invalid, negative, indeterminate results yielded total 17.0% positives initially missed.
      • Positive-negative conversion probability was minimal by 15-20 days after the initial test, and 50% at 28 (95% CI, 27-29) days.

    Study design

    • IgG study: IgG tests evaluated in 224 serially collected serum samples (from 56 patients with confirmed COVID-19).
    • Diagnostics study: evaluation of SARS-CoV-2 molecular assays in dataset covering patients in New York City.
    • Funding: None disclosed.

    Limitations

    • IgG study: small numbers of patients.
    • Diagnostics study: repeat testing in only 15%.