Performance of a Point of Care Test for Detecting IgM and IgG Antibodies Against SARS-CoV-2 and Seroprevalence in Blood Donors and Health Care Workers in Panama

Abstract

Novel severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is the etiologic agent of the ongoing coronavirus disease 2019 (COVID-19) pandemic, which has reached 28 million cases worldwide in 1 year. The serological detection of antibodies against the virus will play a pivotal role in complementing molecular tests to improve diagnostic accuracy, contact tracing, vaccine efficacy testing, and seroprevalence surveillance. Here, we aimed first to evaluate a lateral flow assay's ability to identify specific IgM and IgG antibodies against SARS-CoV-2 and second, to report the seroprevalence estimates of these antibodies among health care workers and healthy volunteer blood donors in Panama. We recruited study participants between April 30th and July 7th, 2020. For the test validation and performance evaluation, we analyzed serum samples from participants with clinical symptoms and confirmed positive RT-PCR for SARS-CoV-2, and a set of pre-pandemic serum samples. We used two by two table analysis to determine the test positive and negative percentage agreement as well as the Kappa agreement value with a 95% confidence interval. Then, we used the lateral flow assay to determine seroprevalence among serum samples from COVID-19 patients, potentially exposed health care workers, and healthy volunteer donors. Our results show this assay reached a positive percent agreement of 97.2% (95% CI 84.2-100.0%) for detecting both IgM and IgG. The assay showed a Kappa of 0.898 (95%CI 0.811-0.985) and 0.918 (95% CI 0.839-0.997) for IgM and IgG, respectively. The evaluation of serum samples from hospitalized COVID-19 patients indicates a correlation between test sensitivity and the number of days since symptom onset; the highest positive percent agreement [87% (95% CI 67.0-96.3%)] was observed at ≥15 days post-symptom onset (PSO). We found an overall antibody seroprevalence of 11.6% (95% CI 8.5-15.8%) among both health care workers and healthy blood donors. Our findings suggest this lateral flow assay could contribute significantly to implementing seroprevalence testing in locations with active community transmission of SARS-CoV-2.

Keywords: COVID-19; Panama; biomarker; diagnosis; immunochromatographic assay; serology.

Figure 1

Panama study sites and health institutions involved. Gray circles on the geographical map of Panama indicate the number of active COVID-19 cases in the areas with the highest incidence of reported cases. Input data June 2020. Source: Panama Ministry of Health. Black arrows indicate the locations of patients and health care workers recruited for this study. The sites included two private hospitals and two public hospitals in Panama and Colón cities. CMP, Centro Médico Paitilla; HPP, Hospital Pacífica Salud; CHDAAM-CSS, Complejo Hospitalario Dr. Arnulfo Arias Madrid- Caja de Seguro Social; CHAMAG-CSS, Complejo Hospitalario Manuel Amador Guerrero-Caja de Seguro Social; CSS-BDC, Caja de Seguro Social Blood Donor Centers.

Figure 2

Schematic representation of study participants and samples distribution. A total of 810 blood samples for detection of IgM and IgG anti SARS-CoV2 antibodies were analyzed for this study. Performance tests included COVID-19 RT-PCR confirmed +/– cases (n = 53) and a pre-pandemic panel of samples (n = 55). For the field study evaluation, a total of 702 participants were enrolled and classified as follows: COVID-19 patients (n = 96), health care workers (n = 351) and healthy volunteer blood donors (n = 255).

Figure 3

Seroprevalence of SARS-CoV2 IgM and IgG in health care workers and healthy volunteer blood donors. A total of 351 healthcare workers (HCW) and 255 healthy volunteer donors (HD) were analyzed by rapid test for detection of anti SARS-CoV2 IgM and IgG antibodies. Each bar represents seroprevalence (%) according to the detection of IgM, IgG, or both IgM and IgG antibodies. Error bars represent the 95% CI.