Patients who tested positive for SARS-CoV-2 antibodies were more likely to have a positive nucleic acid amplification test (NAAT) within 30 days for COVID-19. The association between positive antibody and NAAT results decreased over time. These findings were published in JAMA Internal Medicine.

In this retrospective observational cohort study, researchers analyzed data provided by HealthVerity for 3,257,478 individuals who tested for SARS-CoV-2. The data comprised of more than 50% of commercial antibody and diagnostic testing sites in the United States. Individuals were assessed for health status, symptoms, SARS-CoV-2 antibodies, and COVID-19 NAAT results between December 2018 to August 2020.

Most patients (88.3%) tested negative for antibodies, 11.6% tested positive, and 0.1% (n=2099) had inconclusive results. Stratified by negative and positive antibody status, the mean age of patients were 47.66±17.63 and 44.34±18.09 years, 56.7% and 54.1% were women, 3.5% and 6.3% had symptoms of fever, 0.4% and 1.2% had acute respiratory failure, and 2.0% and 4.3% had viral infections, respectively.


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Patients who were seropositive were more likely to report symptoms of COVID-19 (18.4% vs 0.7%) than patients who were seronegative.

Among the patients who had a subsequent antibody test after a positive result (n=9895), 12.4% tested negative at a test administered up to 30 days after their positive result. At 90 days after, 18.4% retested as negative for SARS-CoV-2 antibodies.

NAATs were administered an average of 3.3 times among patients who were seropositive (n=41,587) and 2.3 times among patients who were seronegative (n=273,735). Positive COVID-19 NAATs were observed among 11.3% of patients within 30 days of a positive antibody test, among 2.7% from 31 to 60 days, and among 1.1% from 61 to 90 days after. The patients who were seronegative tested positive at a rate of approximately 3.0% irrespective of time since antibody assessment.

The ratio of positive NAAT results among seropositive individuals compared with seronegative individuals decreased from 2.85 (95% CI, 2.73-2.97) at day 30, to 0.67 (95% CI, 0.6-0.74) at day 60, 0.29 (95% CI, 0.24-0.35) at day 90, and 0.10 (95% CI, 0.05-0.19) thereafter.

This study may have been limited by not having access to specific data about viral shedding from patients who had a positive NAAT during the period of seropositivity.

The study authors concluded patients who were seropositive for SARS-CoV-2 antibodies were more likely to have a positive COVID-19 NAAT within 30 days of antibody detection, likely due to sustained viral shedding after primary infection. More than a month later, seropositive individuals were at decreased risk for a positive NAAT.

Disclosure: Multiple authors declared affiliations with industry. Please refer to the original article for a full list of disclosures.

Reference

Harvey R A, Rassen J A, Kabelac C A, et al. Association of sars-cov-2 seropositive antibody test with risk of future infection. JAMA Intern Med. Published online February 24, 2021. doi:10.1001/jamainternmed.2021.0366