What did antibody testing reveal in healthcare workers with negative COVID-19 RT-PCR results?

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The researchers noted that misdiagnosis of people suspected of having COVID-19 could contribute to viral transmission, making accurate diagnosis important for containing the disease. RT-PCR is the standard detection method, but it can produce false-negative results. Serological testing has therefore been suggested as a complement to RT-PCR for diagnosing acute infections.

In this observational diagnostic testing study, 15 of 639 unvaccinated healthcare workers tested negative for COVID-19 by RT-PCR but were seropositive for SARS-CoV-2 nucleocapsid protein-specific IgM and IgG antibodies. These 15 participants underwent an additional confirmatory RT-PCR test and a SARS-CoV-2 spike-specific ELISA test. Nine of the 15 tested negative on the second RT-PCR but were seropositive for anti-spike IgM and IgG antibodies and neutralizing antibodies, which the researchers considered confirmation of acute infection.

At the time of sample collection, these nine people were in close contact with patients with confirmed COVID-19, and 77.7% reported COVID-19-related symptoms. The researchers concluded that adding serological tests to the current testing profile could improve diagnostic accuracy and outcomes and help contain viral spread and rapidly prevent future outbreaks.