Canadian Public Health Laboratory Network Statement on Point-of-Care Serology Testing in COVID-19

Abstract

Key points relating to point-of-care serology testing It can take 7-12 days after symptom onset for antibodies to SARS-CoV-2 to develop; therefore, the use of POC serology tests in the early phase of infection can result in falsenegative results at a time when patients are most infectious (i.e. a negative result does not rule out infection) Since POC serology tests do not detect virus, a positive or negative result does not determine whether a person is infectious Positive results may reflect either a past or present infection with SARS-CoV-2 False-positive results may occur if these kits cross react with antibodies from recent or past exposure to other coronaviruses, including human seasonal coronaviruses (HKU1, NL63, OC43, 229E), severe acute respiratory syndrome coronavirus 1 (SARS-CoV-1) or Middle East respiratory syndrome coronavirus (MERS-CoV). Examples of the latter include the following: seroepidemiology-used to better understand the proportion of undiagnosed in the population over time and to provide more accurate data of attack and mortality rates informing targeted diagnostic testing strategies (using PCR testing), where priority would be given to populations/areas with no evidence of immunity detecting seroconversion and assessing immunity in healthcare workers and other essential/frontline workers as an adjunct to PCR for diagnostic testing in patients who are PCR-negative and in the late course of their illness to implement control measures and to effectively manage patients testing high-risk populations exposed to SARS-CoV-2 to assess their risk of developing infection detecting seroconversion as a surrogate for effectiveness of control measures determining, once a vaccine is available, who should be prioritized for earlier vaccination supporting clinical trials that are assessing novel therapies, such as the use of neutralizing antibodies Important considerations for implementing point-of-care serology testing A well validated test, which has been evaluated against a gold standard (viral neutralization assays or another laboratory-based serological assay), is required. Performance characteristics (sensitivity, specificity, positive and negative predictive values, cross-reaction to other coronaviruses) should be established using sera from 1) patients infected with SARS-CoV-2, 2) other respiratory viruses, including seasonal coronaviruses, and 3) healthy controls Adequate training of healthcare workers to administer the test and interpret the result will be required Risk of infection with SARS-CoV-2 and bloodborne infections for the operator must be assessed Provisions must be in place to ensure the capture of 1) testing data for individual patient records and surveillance purposes and 2) requirement for participation in external quality assessment to maintain high-quality testing Conclusion Based on currently available information, the Canadian Public Health Laboratory Network recommends that SARS-CoV-2 POC serological assays not be used for clinical testing in any capacity at this time.