Antibody Self-Testing Program Worked for British Essential Workers

Police officers and firefighters were capable of self-administering COVID antibody tests at home, which had comparable sensitivity and specificity to tests administered by healthcare professionals, a British study found.

Compared to laboratory serology testing, antibody self-testing had a sensitivity of 82.1% (95% CI 77.0-86.0) and a specificity of 97.8%, while rapid antibody tests administered by a nurse in a clinic had a 76.4% (71.9-80.5) sensitivity and 98.5% specificity, reported Helen Ward, PhD, of Imperial College London, and colleagues.

Moreover, self-tests received high marks from the workers, with an acceptability of 97.7%, and 90.0% of those who self-administered the test obtained a valid result, they wrote in Open Forum Infectious Diseases.

Interestingly, the authors noted that participants were more likely to view negative tests as positive, while nurses were more likely to miss “faint positives,” which explains the lower sensitivity of nurse-performed testing.

Self-test finger prick lateral flow immunoassays to detect SARS-CoV-2 antibodies were initially validated among healthcare workers, and were found to be both usable and acceptable in a random sampling of adults, the authors said.

Part of the REal Time Assessment of Community Transmission-2 (REACT-2) program aimed to examine the performance and utility of these self-test kits among non-healthcare professional frontline workers “who do not have specialists training in the use of medical devices.”

The study took place during June and July 2020 among adults in the Airwave Health Monitoring Study, an occupational research cohort of current and former workers in the police force as well as current firefighters. They had to live within about 30 miles of one of six testing sites and could not have a known medical condition that might increase bleeding risk.

Participants were given a self-test for antibodies and a set of instructions. A positive antibody test was defined as IgG positive, and a negative antibody test was IgG negative, regardless of IgM result.

Overall, 5,453 participants attended a clinic visit. Nearly all (88%) of participants were ages 40 and older, two-thirds were men, and 92% were “white British.”

There were 7.4% (95% CI 6.7-8.1) participants with IgG antibodies using laboratory serology testing. The authors noted that 95.2% of results were “concordant” across laboratory serology testing, self-testing and nurse-performed testing. Moreover, 97.2% of self-test and nurse-performed tests had the same results.

Limitations to the data include that it is not generalizable to the population, as police officers and firefighters are not representative of the population of England, and they were likely healthier than the general population. They also may have been familiar with medical procedures, especially emergency service staff.

The authors said that since their data demonstrated that non-healthcare workers could self-administer these antibody tests, “this could then be extended to obtain prevalence estimates in the wider population at low cost, without the need for supervision by a healthcare practitioner” and that self-testing could be used in occupational and community studies of SARS-CoV-2 seroprevalence.