Seroprevalence study of SARS-CoV-2 infection in General Practice in Ireland

Conference:

SAPC ASM 2021 - virtual

Talk Code:

1B.7

Presenter:

Peter Hayes on behalf of Michael E O'Callaghan

Twitter:

@mike0callaghan

Co-authors:

Ryan EJ, Walsh C, Hayes P, Casey M, O’Dwyer P, Culhane A, Duncan J, Harrold P, Healy J, Kerin E, Kelly E, Hanrahan C, Lane G, Lynch B, Meaney P, O’Connell B, Galvin J, Kennedy N, Burke P, O Connell N, Dunne CP, Glynn LG

Author institutions:

University of Limerick

Problem

There is much to learn about SARS-CoV-2 immunity, and serological testing may have a role in tracking viral spread and assessment of our public health efforts. General practice provides an established and accessible means to assess seroprevalence in communities and in at-risk groups.

Approach

This seroprevalence study utilised 2 manufacturers’ point-of-care (POCT) SARS-CoV-2 IgM-IgG combined antibody tests, offered to patients and healthcare workers in general practice. In addition to providing a serum or capillary blood sample, participants were asked whether they had experienced symptoms suggestive of COVID-19 since February 2020, and whether they had a previous polymerase chain reaction (PCR) test for SARS-CoV-2.

Findings

From June 15th to July 10th 2020, 971 participants from 15 general practices were tested. Seroprevalence was estimated at 12.9% in patients attending general practice, and 12.9% in staff working in general practice, with administrative staff having the lowest seroprevalence (6.5%) and nursing staff having the highest (16.3%). These rates are much higher than estimates for the national average (1.7%). Seroprevalence was similar in males and females; was lowest in those 65 years or older; and was elevated in those who had previous symptoms suggestive of SARS-CoV-2 or who had undergone a polymerase chain reaction (PCR) test for SARS-CoV-2 via nasal and throat swab. Sensitivity was 78% and 79% for each test kit type, giving a combined sensitivity of 82%. About a third (32%) of those patients with previous symptoms suggestive of SARS-CoV-2 had undergone a PCR test for SARS-CoV-2 and 17% of those who were seropositive reported no symptoms during the months preceding testing. Average length of time between participants testing positive for SARS-CoV-2 on laboratory PCR testing and testing positive for IgG antibodies was 83 days. Six patients with confirmed COVID-19 infection on PCR testing did not demonstrate presence of IgG antibodies.

Consequences

While not proof of immunity and requiring further study, SARS-CoV-2 POC testing can establish serological prevalence in general practice settings, with a sensitivity of approximately 80%. Persistence of antibodies for an average of 12 weeks in four-fifths of participants with previous COVID-19 infection is encouraging as we learn more about the SARS-CoV-2 immune response.

Submitted by:

Michael O'Callaghan

Funding acknowledgement:

Nil