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I have heard several times now, from both people I personally know and from others who have posted their stories online that they do not qualify for COVID-19 testing.

From the stories I have heard, to qualify you have to: 1. Had contact with a known case of COVID-19 2. Been to a country heavily infected with COVID-19 3. Have symptoms that have progressed to the point where hospitalization is required

We now have a reported 1339 cases in the US with likely many more undiagnosed by medical professionals or the CDC.

Why, when we are in a state of pandemic and all countries scrambling to get a handle on the virus, are clinics, primary cares, and even hospitals not administering tests to those who exhibit symptoms unless one of these other criteria are met?

With an incubation period of 2-14 days, it is entirely possible to have contact with someone who has it and not know you got it from them.

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    Quite simply the USA failed the test at testing. Testing is the first step and in all likelihood they will fail the next steps too. Figuratively their currency is stamped "One nation under God" in reality there are 52 health divisions with no command and control. A rudderless ship if you will. – WinEunuuchs2Unix Mar 13 at 2:19
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There's yet another reason: a test can provide only a certain amount of information gain. If the probability to have contracted Covid-19 before the test is too low, even though we know more after the test we may not be able to draw practical conclusions that are any different from the recommendations without test. In other words, if the recommendation goes from "stay at home and avoid contact to others" to "stay at home and avoid contact to others" the test would be wasted.

The Covid-19 tests are not suitable for screening purposes (i.e. searching for infections among a population where infections are [still] very rare). They are to sort out who is infected and who isn't among high-risk populations where 1 in 10 (or more) are actually infected.


You may want to look at my longish answer to How accurate are coronavirus tests? for relevant background.


E.g., with the newly emergency approved Roche test, we may say that a positive test result increases the odds of having Covid-19 by factor of somewhere around 30 - 100, a negative result decreases the odds by a factor of 1/50 - 1/17.

If you are in a risk group with a prevalence of 8 %, the pre-test odds of 8 : 92

  • increase to (240 to 800) : 92 or a post-test probability of having Covid-19 of 70 to 90 % with a positive test result, and
  • decrease to 8 : (4600 to 1564), i.e. the post-test probability of having Covid-19 is somewhere around 0.5 to 0.2 %

These post-test probabilities allow practical conclusions: if you're negative, you're fine and can be let to meet the public, if you're positive you need to go to quarantine and/or treatment.

8 % prevalence is my guesstimate for those who are currently (Mar 15th) tested in the US (and incidentally, also in Germany).

Now consider the overall US population. With currently 1629 cases and a population of 328 mio., we'd get pre-test odds of 1629 : 328 mio*.

The test results change this to

  • positive result: (27700 to 162900) : 328 mio or a post-test probability of having Covid-19 of 0.008 to 0.005 %
  • negative result: we don't even need to calculate this, because the pre-test probability was only 0.0005 %, post-test probability is lower.

Even if we assume that there's a dark number of yet unknown Covid-19 cases, say, a factor 20 over the known cases, the post-test probabiliy after a positive test is about 0.2 % to 1%.

What would be the practical conclusion? Well, probably that the positive case should stay at home as much as possible and avoid contacts. Certainly not that they can rely on acquiring immunity against SARS-CoV-2.

Even for low risk groups who have flu-like symptoms but no known contact to Covid infected people (or other high-risk situations) the pre-test probability of having Covid is too low to allow the test to make a meaningful difference: after all, even if it is "only a common flu", they should stay at home, get well and not infect others meanwhile. While the pre-test probability is likely to increase (because more people get infected), in order to keep the health system/hospitals working the recommendation will probably not change: stay at home in self-quarantine as long as the symptoms are mild, so that the health system is not burdened by cases that get well on their own.

We may also say that were the whole US population to be tested in that situation, the 32500 true cases of Covid would be drowned in 3 - 10 mio. false positve cases.


*328 mio - 1629 ≈ 328 mio

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  • Would you mind posting a link to this answer at a (so-far) unanswered question I posted a few days ago? Just found your interesting response here, and it appears it may be just as relevant there. Thank you. medicalsciences.stackexchange.com/questions/21594/… (Brand-new here, so apologies if this communication is improper use of commenting, or if there are procedures in-place to refer or combine similar topics.) – revans19 Mar 24 at 4:39
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CDC guidelines for when patients should be tested have changed since the ones you list. CDC now says:

Clinicians should use their judgment to determine if a patient has signs and symptoms compatible with COVID-19 and whether the patient should be tested. Most patients with confirmed COVID-19 have developed fever1 and/or symptoms of acute respiratory illness (e.g., cough, difficulty breathing). Priorities for testing may include:

Hospitalized patients who have signs and symptoms compatible with COVID-19 in order to inform decisions related to infection control.

Other symptomatic individuals such as, older adults (age ≥ 65 years) and individuals with chronic medical conditions and/or an immunocompromised state that may put them at higher risk for poor outcomes (e.g., diabetes, heart disease, receiving immunosuppressive medications, chronic lung disease, chronic kidney disease).

Any persons including healthcare personnel, who within 14 days of symptom onset had close contact with a suspect or laboratory-confirmed COVID-19 patient, or who have a history of travel from affected geographic areas (see below) within 14 days of their symptom onset.

This is a broad definition that gives clinicians the freedom to judge, though it still emphasizes priority for cases similar to the older guidelines.

However, guidelines and reality may not match. Via NPR:

There's still a big gap between what the federal government is promising and what state and local labs can deliver.

...

...those labs have a limited capacity to test, so some have been turning down doctors' requests.

The novel coronavirus test isn't simple, like the ones for the flu, strep or pregnancy. The kits detecting the coronavirus are configured more for a research lab than a hospital — and certainly can't be run in a doctor's office. It takes four to six hours to perform the tests on patient samples.

Therefore, at this point the main reason that people with symptoms are being denied tests seems to involve a shortage of the tests, and possibly prioritization of tests for other patients. Hopefully these problems will be resolved going forward.

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  • they have meanwhile test kits that are movable - and the result can be told in 30 min. That's why I ask: is this the virus that is spreading or is it the test? – Albrecht Hügli Mar 12 at 16:34
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Because the USA has been extremely poorly prepared for this pandemic there has been a severe shortage of test kits. A number of other egregious errors were made including declining to accept the German test offered to them, or using the South Korean test kits. South Korea have been testing 10,000 people a day which is more than the USA has since the outbreak developed.

In this situation the clinicians have triaged as much as they could to decide who to test developing an evolving set of clinical and epidemiological criteria which have loosened. But what they didn't know was that the virus been likely been circulating in the community for some weeks as community transmission was detected in late February.

At this time the most appropriate response is to self isolate if one develops any respiratory symptoms, and advise close contacts. Because testing has been very limited it is nearly impossible to satisfy the epidemiological criterion of knowing about a contact with the disease.

https://www.nytimes.com/2020/03/10/us/coronavirus-testing-delays.html

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If everyone would like to be tested who shows some symptoms of this infection you could test probably 50% of the population: "me too!" As the capacity of tests is limited it is really necessary that these test kits are reserved for persons that are diagnosed by a doctor. In case of a pandemia - and if this is one - people should keep distance to others, wash their hands and shouldn't go to work if they think they are infected. People with severe symptoms should stay at home and call the doctor and get information by phone.

And save the disinfection solutions and masks for the doctors and medical staff and the ill people.

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Because the CDC won't let them test them. Understand that hospitals can't perform tests for Covid-19--originally only the CDC could. Now, some state laboratories can test. Either way, hospitals can't test people whom the labs don't allow testing for. It's not entirely the hospital's decision.

Keep in mind that some of these restrictions are pretty common sense. For instance, some of these requirements restrict that if you have these symptoms, but we know you have the Flu (which has similar symptoms), then there's no reason to test you for Covid-19. It's pretty reasonable to assume that these symptoms are because of the Flu.

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  • There's data to support your answer. Research labs have developed their own test and detected infections in the community but were shut down by the CDC because these tests had not been validated and passed by the FDA. – Graham Chiu Mar 16 at 5:40

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