The Strategy of Rapid Testing

As the Covid-19 crisis remains out of control, publics around the world can’t help being obsessed with three questions:

  1. What are my chances of getting infected or infecting others?
  2. If infected, what are my odds of dying?
  3. What can I do right now to protect myself and my loved ones?

Mask wearing and sensible physical distancing are the easiest available responses to the 3rd question. Clinicians are getting better at predicting who is most at risk and saving lives, but we are a long way from the kind of predictive diagnostics we need.

However, the biggest problem, arising from a fundamentally flawed testing protocol, is that, at an individual and a population level, we have no idea who among us are infected. We operate with far more fear when we don’t know the answer to the basic question of what are my odds of getting infected or dying.

To do that, we need two strategies:

  1. Pooled testing (e.g. waste water analyses for cities, campuses, and, eventually, buildings) determines the infection rate in a population; and
  2. Rapid point-of-care testing can supplement the lab test to detect which of us are infected.

There are two approaches to rapid point-of-care diagnostic Covid19 testing: at an outpatient clinical setting or at home. Eventually, testing will be done by non-medical personnel following a standard protocol.

The goal is to avoid the delays, the handling risks, and the costs of transporting samples to laboratories. Testing needs to be done where the samples are collected

The best currently available technology for rapid, frequent, inexpensive testing is the Abbott Labs Binax Now Covid-19 test, but we need more options.

Dr. Michael Mina of Harvard T.H. Chan School of Public Health has said that the most credible testing strategy is frequent, inexpensive, rapid response at-home testing with a paper strip.

This is why he strongly advocates it:

The strength of this system is that it would actually abrogate the need for contact tracing, says Mina. “If your goal is not to have a heavy hand over the population” (implementing onerous public-health restrictions on businesses and recreational activity), this is the way to do it, he explains, because it strips away “all of that complexity.” Most people who test positive will have done so before they become infectious, and can easily self-quarantine for the six days or so until they cease being infectious.

By contrast, the current testing protocol touches too few of us, takes too long for results, and catches people so late in the infection process that it delivers a positive result when they are no longer at risk to themselves or others.

Additional vendors are seeking FDA approval for rapid tests, but they are not yet in the market. However, the Abbott Labs test can be used in the meantime.

Another promising rapid point-of-service testing process is being tested: breathalyzers to detect the presence of the virus within 15-30 seconds. These tests are between 85-90% effective. They used different approaches that do not overlap.

If the data were collected from these tests over several days, the amount of data required for close to 100% certainty from the tests alone would actually decline. Confidence levels would increase as other data is combined with the data from the two testing methodologies.

There are other testing methodologies that require a saliva sample, but they require the saliva to be analyzed in a lab. Eventually, this could be a 3rd independent rapid test method.

Whatever the status of vaccines, antiviral therapies and convalescent plasma, knowing our true level of risk will give us more peace of mind and a more realistic ability to protect ourselves in the meantime.