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. 2021 Mar 30;34(4):437-441.
doi: 10.1080/08998280.2021.1895959.

Screening for SARS-CoV-2 via PCR and serological testing in asymptomatic healthcare workers

Taimur Safder  1 , Peter A McCullough  1   2   3   4 , Kevin R Wheelan  1   3   4 , Gelareh Rahimi  1 , Sandra Zurawski  5 , Gerard Zurawski  5 , Jinghua Gu  5 , Xuan Wang  5 , Uthra Balaji  5 , Mezgebe Berhe  2   3   6 , Laura Clariday  1 , Rebecca Baker  1 , Kristen Chionh  1 , Giselle Carino  1 , Uriel S Sandkovsky  3   6
Affiliations

Screening for SARS-CoV-2 via PCR and serological testing in asymptomatic healthcare workers

Taimur Safder et al. Proc (Bayl Univ Med Cent). .

Abstract

The prevalence and seroconversion rate of SARS-CoV-2 infection among asymptomatic health care workers in the US is unclear. Our study utilized real-time polymerase chain reaction (RT-PCR) SARS-CoV-2 testing and serological evaluation to detect IgG antibodies specific to SARS-CoV-2 antigens in asymptomatic health care workers. A total of 197 subjects with a mean age of 35 years were recruited into the study. While most (67%) reported prolonged contact with known COVID-19 patients, only 8 (4.2%) tested positive on RT-PCR and 23 (11.7%) had detectable levels of IgG antibody to SARS-CoV-2. Out of 19 subjects with detectable IgG antibody at week 1, 11 (57.9%) lost their antibody response by week 3. No statistically significant difference was found in baseline characteristics or exposure status between subjects with positive and negative results on RT-PCR or antibody positivity. In conclusion, we found a low incidence of PCR positivity for SARS-CoV-2 in a high-risk group. This likely demonstrates the effectiveness of proper personal protective equipment use and low transmission risk in health care settings. The detectable IgG antibody titer was low, and a significant portion of subjects lost their antibody response on repeat testing. This may mean that antibody response in asymptomatic patients is categorically different than in symptomatic hospitalized patients with COVID-19.

Keywords: Antibody; COVID-19; PCR testing; SARS-CoV-2; healthcare workers; serology.

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Figures

Figure 1.
Figure 1.
A flowchart of patients with detectable IgG antibody to SARS-CoV-2 in the context of PCR positivity as well as when the antibody test became positive and if it was sustained.
Figure 2.
Figure 2.
A subject’s detectable antibody to RBD antigen signal (in pink) on the first week of testing (T0) and the loss of signal on testing 2 weeks later. Two different sets of negative controls (light and dark green) and a positive control (orange) are shown for comparison. The signals from positive control samples were considerably higher than those of the study subjects.
Figure 3.
Figure 3.
A plot of patients who had detectable IgG antibody (plotted according to either N or RBD IgG positivity) at two different time points. Most patients had a weak positive signal to begin with, which decreased or was lost at testing 2 weeks later.
Figure 4.
Figure 4.
Weekly hospital census of COVID-19 patients at Baylor University Medical Center with the time of study recruitment noted.
See this image and copyright information in PMC

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