HealthDay News — The diagnostic specificity of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) serologic assays varies, and sensitivity is poor during the first 14 days of symptoms, according to a study published in Clinical Chemistry.

Mei San Tang, MD, from the Washington University School of Medicine in St. Louis, and colleagues compared two commercial SARS-CoV-2 immunoglobulin G assays. A total of 103 specimens from 48 patients with polymerase chain reaction-confirmed SARS-CoV-2 infections and 153 control specimens were analyzed using serologic assays by Abbott and EUROIMMUN.

The researchers found that the Abbott SARS-CoV-2 assay had diagnostic specificity of 99.4% and sensitivity of 0.0%, 30.0%, 47.8%, and 93.8% at <3, 3 to 7, 8 to 13, and ≥14 days post-symptom onset. On the EUROIMMUN assay, diagnostic specificity was 94.8% and 96.7% if borderline results were considered positive and negative, respectively. If borderline results were considered positive, the diagnostic sensitivity was 0.0%, 25.0%, 56.5%, and 85.4% at <3, 3 to 7, 8 to 13, and ≥14 days , respectively. The qualitative concordance was 0.83 between the assays.

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“Our results also demonstrate low sensitivity for detecting SARS-CoV-2 antibodies before 14 days post-symptom onset on both assays,” the authors write. “This argues that serologic status should not be assessed until 14 days post-symptom onset and confirms that molecular assays should remain the primary method for COVID-19 diagnosis.”

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One author disclosed financial ties to the biotechnology industry.

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