key: cord-316880-hbw6jbz5
authors: Sutton, Melissa; Cieslak, Paul; Linder, Meghan
title: Notes from the Field: Seroprevalence Estimates of SARS-CoV-2 Infection in Convenience Sample — Oregon, May 11–June 15, 2020
date: 2020-08-14
journal: MMWR Morb Mortal Wkly Rep
DOI: 10.15585/mmwr.mm6932a4
sha: 
doc_id: 316880
cord_uid: hbw6jbz5

nan

to the Oregon State Public Health Laboratory for testing with the Abbott Architect Laboratories SARS-CoV-2 IgG immunoassay. Abbott Laboratories (Abbott Park, Illinois) reports a sensitivity of 96.8% at ≥14 days after a positive polymerase chain reaction test result and specificity of 99.1%-100% (1) . Results from actual use support the reported analytical performance of this test (2) .

Although 18 facilities were initially recruited, another facility was added through the same sequential approach because one facility was only able to submit 15 specimens. The facilities' locations were approximately representative of the geographic distribution of Oregon's population. During May 11-June 15, 2020, a total of 898 venous specimens (average from each facility = 47; range = 15-50) were collected from the 19 facilities; one specimen was discarded because of a laboratory error. This activity was reviewed by CDC and was conducted consistent with CDC policies and procedures, and institutional review board clearance was not required.** Stata (version 15.1; StataCorp) was used for all analyses.

Antibodies to SARS-CoV-2 were detected in nine of 897 specimens, yielding an unadjusted seroprevalence of 1.0% (95% confidence interval = 0.2%-1.8%). Antibodies were not detected in any specimens from the 29 persons aged ≤17 years. Seroprevalence generally increased with age (chi-squared test for trend, p = 0.049) (Table) .

The estimated seroprevalence of SARS-CoV-2 antibodies in a convenience sample of adult Oregonians was approximately 10 times the measured cumulative COVID-19 incidence obtained by nucleic acid testing, consistent with results from seven other U.S. states and geographic areas (4). This convenience sample, obtained from patients interacting with health care systems throughout the state, is not necessarily generalizable to the entire state population. Limitations of seroprevalence testing include false positivity in settings of low background prevalence such as Oregon, lack of antibody development by some infected persons, and in others, waning of antibodies to undetectable levels. The data suggest that a substantial number of COVID-19 cases in Oregon have gone undiagnosed and not reported and that a large portion of Oregon's population remains susceptible to COVID-19 infection. Although the sample size was small, a pattern of increasing seroprevalence with age was observed. These findings are similar to those reported in a recent survey in neighboring Idaho (1). Follow-up surveillance studies are planned in Oregon to reassess cumulative incidence as the pandemic progresses. 

Performance characteristics of the Abbott Architect SARS-CoV-2 IgG assay and seroprevalence in

Population point prevalence of SARS-CoV-2 infection based on a statewide random sample-Indiana

CDC Field Surveyor Team. Estimated community seroprevalence of SARS-CoV-2 antibodies-two Georgia counties

Seroprevalence of antibodies to SARS-CoV-2 in 10 sites in the United States

All authors have completed and submitted the International Committee of Medical Journal Editors form for disclosure of potential conflicts of interest. No potential conflicts of interest were disclosed.