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The role of COVID-19 antibody testing for employers

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Authors:
Jacquelyn W Chou, MPP, MPL - Senior Director, PRECISIONheor
Caroline Huber, MPH – Director, PRECISIONheor
Jennifer Millard, MBA – Vice President, PRECISIONheor

After the widespread implementation of stay-at-home and social distancing orders to stem the spread of COVID-19, states and municipalities across the United States and beyond are reopening for business. Amid the calls to jump-start the economy, employers must determine how to reopen and keep their employees and customers safe. Many employers have started turning to temperature checks and looking into testing options to determine which of their staff may be infected and which might be considered safe to work. Antibody testing has increasingly become part of the conversation, but may be a poor tool to support reopening plans.

What is testing?

Testing in the context of the COVID-19 pandemic refers to two types. The initial focus was on increasing the capacity and availability of viral polymerase chain reaction (PCR) testing, which identifies active infections. The second type of testing is antibody testing, which identifies patients who previously have been infected with COVID-19, recovered, and developed antibodies. Due to the relatively easier access to antibody testing, employers have started to explore the use of antibody testing as part of their COVID-19 plans. However, two key issues remain unresolved before antibody testing can be truly useful for an employer.

Remaining challenges for antibody testing

The primary concerns with currently available antibody tests are quality and reliability. There are over 100 antibody tests on the market, with the US Food and Drug Administration (FDA) having previously taken a hands-off approach to regulation. With all diagnostic tests, there are two important metrics: sensitivity and specificity.

Sensitivity refers to the test’s ability to accurately identify true positives – people with the COVID-19 antibody. A 90% sensitivity would mean the test incorrectly identifies 1/10 true positives as negative. Specificity refers to the test’s ability to accurately identify true negatives – people without the COVID-19 antibody. A 90% specificity means that 1/10 patients who are negative are inappropriately identified as having the antibody.

The antibody tests on the market have a broad range of sensitivity and specificity, raising concerns of both false positives and false negatives. Many of the current tests also fail to distinguish between the novel coronavirus and the virus that causes the common cold. An employer looking to purchase an antibody test needs to be sure of the accuracy of results, with greater specificity likely more important as a false positive would result in greater harm than a false negative.

Second, even assuming highly accurate tests, the degree of immunity to COVID-19 after infection and recovery is unknown. Some viruses, such as chicken pox, have a very low probability of reinfection after an initial infection or vaccine. Other viruses, such as the flu, have a number of mutations and strains, with little immunity conferred. In a recent study, van Dorp and colleagues identified multiple strains of COVID-19, as well as multiple genetic mutations, suggesting that COVID-19 may be more similar to the flu than chicken pox. This calls into question the utility of a positive antibody result for employers. We currently have insufficient data to suggest that someone testing positive for antibodies would not be reinfected or would not otherwise further transmit the virus if exposed. For an employer, just knowing which workers have the COVID-19 antibody still cannot tell them whether or not those workers are safe from future infection or spreading infection.

The outlook

With these two remaining challenges, the utility of implementing widespread antibody testing for employers is low and likely not worth the cost. However, these are not insurmountable problems. The FDA has already stepped in to help regulate the antibody testing market. On May 4, the FDA issued revised guidance requiring testing manufacturers to submit validation data in their applications for emergency use authorizations and establishing thresholds for specificity (95%) and sensitivity (90%). The FDA has also publicized test performance data online, as have other third-party entities, allowing employers to identify which test they might consider to be more accurate for use with their workforce.

Further, large employers may want to consider participating in the budding industry of COVID-19 data registries. Initial data about COVID-19 predominantly came from single institution/department samples or case studies. However, the importance of being able to aggregate data has become clear. With a centralized COVID-19 registry, we will gain a better understanding of the virus and its natural history as well as answer the important question of reinfection. The benefit for employers to have more certainty regarding reinfection would be high.

The COVID-19 pandemic has been unprecedented in terms of its human toll and economic impacts. Although governments move quickly on initiatives to flatten the curve, understanding how tools, such as antibody testing, can and cannot be used to reopen the economy is critical.

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