COVID-19 Seroprevalence in a Mixed Cohort of SARS-CoV-2 PCR Positive and
Exposed Subjects
Abstract
1.1 Background Early in the SARS-CoV-2 pandemic, polymerase
chain reaction (PCR) testing was reserved for symptomatic patients.
However, many infections were asymptomatic or mildly symptomatic.
Positive serologic antibody (Ab) testing is theorized to be a marker of
prior infection, allowing for identification of true burden of disease
and establishing links between outbreaks. 1.2 Objective Assess
serologic testing in subjects after PCR testing and compare
seropositivity rates of household vs. non-household close contacts.
1.3 Methods We identified subjects who were PCR-positive
between March 2020 and May 2021. Index cases and close contacts then
underwent serologic testing for IgG against SARS-CoV-2 nucleocapsid
N-protein. 1.4 Results One-hundred-and-thirteen subjects
underwent serologic testing with a sensitivity of 65.0%, specificity of
78.9%, positive predictive value of 92.9%, and negative predictive
value of 34.9%. Index cases comprised 20.5% of subjects, and 73.9%
were seropositive (p=0.01). Close contacts included 72% household
contacts and 28% non-household contacts. One seropositive case had no
prior PCR and four were PCR negative. No statistical difference existed
in seropositivity between household and non-household contact (53.1%
vs. 43.8%, p=0.4). 1.5 Conclusions Testing for IgG against
SARS-CoV-2 N-protein may identify previously unrecognized infections in
the community. Seropositivity rates of household vs. non-household
contacts were not significantly different, and >50% of
household contacts were seropositive.