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Risk Reduced for Positive NAAT Result With SARS-CoV-2 Antibodies

Patients with positive antibody test initially more likely to have positive NAAT result but less likely after 30 days

blood samples

THURSDAY, Feb. 25, 2021 (HealthDay News) -- Having severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) antibodies is associated with a reduced risk for future infection, according to a study published online Feb. 24 in JAMA Internal Medicine.

Raymond A. Harvey, M.P.H., from Aetion Inc. in New York City, and colleagues examined evidence of SARS-CoV-2 infection based on a diagnostic nucleic acid amplification test (NAAT) among patients with positive versus negative test results for antibodies. Postindex diagnostic NAAT results were examined, with infection defined as a positive diagnostic test result, measured in 30-day intervals. Data were included for 3,257,478 unique patients with an index antibody test.

The researchers found that 88.3 and 11.6 percent of the patients had a negative and positive index antibody result, respectively. Compared with those with a positive result, patients with a negative antibody test result were older. During the follow-up period, 18.4 percent of the index-positive patients converted to seronegative. For individuals who had a positive antibody test at index versus those with a negative antibody test, the ratio of positive NAAT results was 2.85, 0.67, 0.29, and 0.10 at 0 to 30, 31 to 60, 61 to 90 days, and more than 90 days, respectively.

"The presence of antibodies to SARS-CoV-2 is associated with a reduced risk of having a subsequent positive NAAT results, which may be a proxy representing a new infection or may represent continued viral shedding depending on the context and timing," the authors write.

Several authors disclosed financial ties to the biopharmaceutical industry.

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