Earlier this week, The Infectious Disease Society of America (IDSA) reassessed the utility of antibody tests with respect to COVID-19 surveillance and diagnostics.
More directly, the researchers stated that anti-body testing kits (alternatively referred to as serology tests) need to evidence a clinical sensitivity of over 99.5% to be useful to individual diagnoses and if the tests are going to aid herd immunity analysis, they need to accurately report positive results 96% of the time and correctly report negative results a minimum of 99.5% of the time.
Currently, very few available testing kits meet these criteria. Because of this (among other things) some health systems have advised populations against requesting serologic testing unless they are disproportionately affected by the novel coronavirus.
In direct contrast with initial directions calling for anti-body tests for anyone who came into contact with an infected patient for more than 15 minutes—irrespective of a lack of characteristic symptoms, the Centers for Disease Control and Prevention’s most recent guideline says there isn’t necessarily a need for an antibody test if you’re not a vulnerable individual.
The agency recognizes the following conditions as those that would justify the need for an anti-body test:
- Chronic kidney disease
- COPD (chronic obstructive pulmonary disease)
- Immunocompromised state (weakened immune system) from solid organ transplant
- Obesity (body mass index [BMI] of 30 or higher)
- Serious heart conditions, such as heart failure, coronary artery disease, or cardiomyopathies
- Sickle cell disease
- Type 2 diabetes mellitus
- The elderly (particularly those over the age of 50)
Even if you might have come into contact with an infected COVID-19 patient, the CDC contends that your health care provider or state or local public health officials should be the ones to determine whether or not you require testing if you do not fall into any of the conditions above.
“The Food and Drug Administration has not authorized antibody testing to diagnose COVID-19, and the CDC does not currently recommend using antibody testing for diagnosis of any infection. In certain situations, antibody tests may be used in conjunction with viral detection tests to support clinical assessment of persons who present late in their illnesses,” the CDC writes on their website. “In addition, if a person is suspected of having a post-infectious syndrome caused by COVID-19 (e.g., Multisystem Inflammatory Syndrome in Children; MIS-C), antibody tests may be used to determine prior infection. Antibody tests for COVID-19 can play an important role in the surveillance and epidemiologic studies, which can provide insights into the transmission dynamics of the virus among the general population. Unlike direct viral detection methods that can detect currently infected persons, antibody tests help determine whether the individual being tested was previously infected, even if that person never showed symptoms.”
In the four short days since the new guideline was published, lawmakers and academicians alike have expressed dissenting concerns.
Many have pointed out the CDC’s own appreciation of the 40% of SARS-CoV-2 carriers that remain asymptomatic for the entire duration of infection.
These were previously determined to be super-spreaders; young otherwise healthy individuals attending densely populated events with little precautions because they had no reason to believe they were ill.
Early Wednesday morning Assistant Secretary of the United States Department of Health and Human Services, Dr. Brett Giroir clarified the factors that informed the CDC’s decision to CNN:
“The updated Guidance places an emphasis on testing individuals with symptomatic illness, those with a significant exposure or for vulnerable populations, including residents and staff in nursing homes or long term care facilities, critical infrastructure workers, healthcare workers and first responders, and those individuals (who may be asymptomatic) when prioritized by public health officials.”
It’s true, the majority of antibody testing kits currently available are linked with a 10% chance of administering a false negative and a false positive, but that’s why researchers aren’t counting on them for individual diagnosis.
Anti-body tests, which detect important proteins in our blood that fight off antigens, appear to be reliable ways to gauge a community’s progress as a whole. We need measures like these to assess risk during shutdown easing.
The Harvard Global Health Institute reports that counties should only consider reopening schools if they evidence 25 cases of Covid-19 per 100,000 people.
Similarly, The World Health Organization cautions against traditional attendance if a county surpasses 5% of positive cases.
Harvard intends on allowing 40% of its 6,700 undergraduates to live on campus safely by supplying them with antibody tests every two days.
“I am worried that this is just a way to slow down testing and that would clearly be not good,” Dr. Carlos del Rio, infectious disease specialist and associate dean of Emory University School of Medicine said of the newly updated guidelines in a release. “We don’t want to decrease the amount of testing. We want to decrease cases by decreasing transmission, not by decreasing testing.”
“The updated recommendations by the CDC stating that asymptomatic people may not need to be tested even if they have been in close contact with someone known to have the virus are very troubling as this is the exact patient population that should be tested,” Dr. Ravina Kullar, an infectious disease expert in California, explained to Fox News. “An individual has a high probability of getting the virus from close contact with someone that has had the virus; why would he/she not be recommended to get tested?”
Hopefully, the CDC can choreograph a less divisive solution to the fears expresses on behalf of cooperating parties.