Unless you fall into these 3 categories, antibody tests might not tell you much

In a recent COVID-19 roundup, Ladders cited Harvard University’s new testing initiative.

In order for 40% of its 6,700 undergraduates to safely return to campus, resident health officials will offer antibody tests based on four requirements:

  1. You have had COVID-19 symptoms. 
  2. You are recovered.
  3. You need to know your antibody status for decision-making. 
  4. You have a Primary Care Physician (PCP) at HUHS. 

Establishments across the country are mulling over similar measures to prepare for shutdown easing.

While the majority of experts condone the increased use of antibody tests, the same are mindful of their limited potential.

Remember, antibody tests (alternatively referred to as serology tests) don’t detect the presence of a virus itself but the proteins in our blood that fight it off.

A positive result is a pretty good indicator that your immune system has encountered SARS-CoV-2 but it does not tell you how long you will remain defended against it--saying nothing of the 10% chance for false positives and negatives associated with novel coronavirus testing kits.

All of these parameters and more were recently explored in The Infectious Disease Society of America‘s (IDSA) updated guidelines on the diagnosis of COVID-19 via serologic testing.

If epidemiologists are going to factor anti-body test results into individual diagnoses, tests need to evidence a clinical sensitivity over 99.5%.

If authorities are going to factor antibody tests into herd immunity analysis, tests the IDSA requires tests to be report positives accurately 96% of the time and correctly report negative results a minimum of 99.5% of the time.

Current most serology tests do no meet any of the aforementioned requirements but Elisa or CIA (chemiluminescence immunoassay) tests offer the most reliable results available.

“The availability of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) serologic testing has rapidly increased. Current assays use a variety of technologies, measure different classes of immunoglobulin or immunoglobulin combinations, and detect antibodies directed against different portions of the virus. The overall accuracy of these tests, however, has not been well-defined,” the researchers wrote in the report’s abstract. “Based on available evidence, detection of anti-SARS-CoV-2 antibodies may be useful for confirming the presence of current or past infection in selected situations. The certainty of available evidence supporting the use of serology for either diagnosis or epidemiology was, however, graded as very low to moderate.”

The organization goes on to index three primary functions of COVID-19 antibody tests:

  1. The evaluation of patients with a high clinical suspicion for COVID-19 when molecular diagnostic testing is negative and at least two weeks have passed since symptom onset
  2. The assessment of multisystem inflammatory syndrome in children
  3. For conducting zero surveillance studies

This conclusion advises against relying on antibody test results to lessen countermeasures ahead of a vaccine because the results say very little about transmission risks.

Roughly 40% of the population will not exhibit symptoms characteristic of COVID-19 during the entire duration of infections. A comparable majority of people already experience viral clearance in the window in which anti-body tests are the most educative (three to four weeks after the onset of symptoms).

PCR tests, on the other hand, are designed to pick up antigens directly by scanning for their viral RN–which will be detectable in the infected person before antibodies form and symptoms of the disease are present.

“At the moment the majority of the current Covid-19 tests that all the reports are coming from are using PCR,” explained the University of Sussex senior lecturer in microbiology Dr. Edward Wright in a media release. “They detect the genetic information of the virus, the RNA. That’s only possible if the virus is there and someone is actively infected.”

Antibody tests still offer a myriad of useful information as far as contact tracing is concerned.

Be sure to consult a medical professional if you meet any of the requirements presented in IDSA’s new guideline.