Seroprevalence of Novel Coronavirus SARS-CoV-2 at a Community Hospital Emergency Department and Outpatient Laboratory in Northern Orange County, California

J Racial Ethn Health Disparities. 2021 Dec;8(6):1551-1555. doi: 10.1007/s40615-020-00918-0. Epub 2020 Nov 23.


Introduction: The severe acute respiratory syndrome related coronavirus 2 (SARS-CoV-2) has infected more than 20 million people worldwide, and the spread is most prevalent in the USA, where California had accounted over 240,000 cases in the initial 5 months of the pandemic. To estimate the number of infected persons in our community, we conducted a cross-sectional study to estimate seroprevalence of SARS-CoV-2 infection.

Methods: This cross-sectional study evaluated the presence of immunoglobulin G, antibody for SARS-CoV-2 during the time period of July 15, 2020, to July 27, 2020. Testing was done on serum samples from patients who had visited affiliated outpatient clinics or our emergency department. Additionally, we collected age, gender, ethnicity, race, and location of testing.

Results: Eight hundred sixty-five tests were included in the study. The outpatient clinics cohort accounted for 56% of results and emergency department (ED) contributed 44%. The positive percentage of SARS-CoV-2 test was 9.4% (95% CI: 0.08-0.12). The positivity rates of the outpatient (5.6%) and ED (14.2%) setting differed. The prevalence of SARS-CoV-2 IgG was greatest in those that identified as Hispanic/Latino, 18.1% versus 13.4% in other groups. Specifically compared to the non-Hispanic/Latino population, the prevalence was significantly higher, with a relative risk of 2.73 (95% CI: 1.8-4.1), p < 0.0001.

Conclusion: The low antibody positivity rate in the community indicates the need for a vaccine. The Hispanic/Latino patient population should be considered for increased education on preventing transmission and acquisition of COVID-19 as well as being considered as a priority for vaccination once a vaccine is available.

Keywords: COVID-19; Immunoglobulin G; SARS-CoV-2.

MeSH terms

  • Adolescent
  • Adult
  • Aged
  • Aged, 80 and over
  • Ambulatory Care*
  • Antibodies, Viral / blood
  • COVID-19 / epidemiology*
  • COVID-19 / ethnology
  • COVID-19 Testing
  • California / epidemiology
  • Child
  • Cohort Studies
  • Cross-Sectional Studies
  • Emergency Service, Hospital*
  • Female
  • Health Status Disparities
  • Hispanic or Latino / statistics & numerical data
  • Hospitals, Community*
  • Humans
  • Immunoglobulin G / blood
  • Laboratories*
  • Male
  • Middle Aged
  • Prevalence
  • Risk Factors
  • SARS-CoV-2 / immunology
  • SARS-CoV-2 / isolation & purification
  • Seroepidemiologic Studies
  • Young Adult


  • Antibodies, Viral
  • Immunoglobulin G