Category Archives: Positivity Rate – High

Making coronavirus testing easy, accurate and fast is critical to ending the pandemic – the US response is falling far short

Posted on by • Posted in 2020 Election Issues, Asymptomatic Transmission, Clinical Testing, Contact Tracing, Coronavirus, Crisis, Crisis Management, Economic Crisis, Economic Recovery, Evidence-based Leadership, Evidence-Based Plan, Evidence-Based Policy, Failure, False Hope, False Narrative, Infection Control, Infection Control Plan, Infectious Virus, Leadership Decentralized, Misinformation, Misinterpret, Mislead, Misleading, Mistake, Mistrust, Mixed Message, Mortality, National Strategy, Pandemic, Personal Protective Equipment (PPE), Positivity Rate, Positivity Rate - High, Public Health, Public Opinion, Public Perception, Public Safety, Public Trust, Quarantine, School Reopening, Scientists, Social Distancing, World Health Organization (WHO) • Leave a comment

https://theconversation.com/making-coronavirus-testing-easy-accurate-and-fast-is-critical-to-ending-the-pandemic-the-us-response-is-falling-far-short-142366

Making coronavirus testing easy, accurate and fast is critical to ...

For many people in the U.S., getting tested for COVID-19 is a struggle. In Arizona, testing sites have seen lines of hundreds of cars stretching over a mile. In Texas and Florida, some people were waiting for five hours for free testing.

The inconvenience of these long waits alone discourages many people from getting tested. With the surge in cases, many public testing sites have been reaching maximum capacity within hours of opening, leaving many people unable to get tested for days. Those that do get tested often face a week-long wait to get their test results.

Every person who isn’t tested could be spreading COVID-19 unknowingly. These overstretched testing programs are a weak link in the U.S. pandemic response.

I study public health policy to combat infectious disease epidemics. The key to overcoming this pandemic is to slow transmission of the virus by preventing contagious people from infecting others. A widespread quarantine would accomplish this, but is economically and socially burdensome. Testing offers a way to identify contagious people so they can be isolated to prevent the spread of the disease. This is especially important for COVID-19 because an estimated 40% or more of all people infected with SARS-CoV-2 have few or no symptoms so testing is the only way to identify them.

Some states are doing much better than others. But as a whole, the U.S. is falling far short of the amount of testing needed to control the pandemic. What are the challenges the U.S. is facing? And what is the way forward?

Testing should be free, easy, fast and accurate

The ultimate goal of testing is for everyone, regardless of symptoms, to know at all times whether they are infected with the coronavirus. To achieve this level of testing, tests should be free, very easy to perform and provide accurate results quickly.

Ideally, free COVID-19 tests would be delivered to everyone directly. The tests would be simple to perform – like a saliva test – and would give a perfectly accurate result within minutes. Everyone could test themselves weekly or anytime they were going to be in close contact with other people.

In this ideal scenario, most, if not all, contagious people would be detected before they could spread the virus to others. And because of the rapid results, there would be no burden of quarantining between doing the test and getting the result.

Researchers are working on better-quality tests, but access is a problem of infrastructure, not science. Right now, nowhere in the U.S. comes close to meeting surging demand for testing.

One of the worst cases: Texas

The difficulty of getting a COVID-19 test varies by state, but currently, people in Texas face some of the biggest obstacles, which results in far fewer tests being done than is needed to control the pandemic.

First, Houston – which is experiencing a surge in cases – and many testing sites across the state recommend or offer testing only to people who have symptoms, were exposed to a COVID-19 case or are a member of a high-risk group.

Even people recommended for testing still face challenges. It is possible to request an appointment for a free COVID-19 test, but testing facilities can handle only so many patients a day and testing slots fill up quickly. Even if someone gets an appointment, they may face an hours-long wait at the testing site.

Finally, public health experts recommend that people who may have been exposed to COVID-19 should quarantine at home for 14 days or until they receive a negative test result. In Texas, patients are supposed to get results through an online portal in three to five days, but many labs have been taking seven to nine days to return results. These long delays mean people face a much higher burden of quarantining while waiting for results.

All of these challenges make it clear that Texas is simply not testing enough people to keep the spread of COVID-19 in check.

To gauge the success of COVID-19 testing programs, epidemiologists use a measure called test positivity. This is simply the percentage of tests that come back positive. The lower the test positivity, the better, because that means very few cases are going undetected. A high test-positivity rate is usually a sign that only the sickest people are getting tested and many cases are being missed.

The World Health Organization guidelines say that if more than 1 out of 20 COVID-19 tests comes back positive – a test positivity of more than 5% – this is an indication that a lot of cases are not diagnosed and the epidemic is not under control. 

Texas currently has a test-positivity of around 16%, which means that a lot of infected people are not getting tested and may be unknowingly spreading the disease.

One of the best cases: New Mexico

In stark contrast to Texas is New Mexico, which has one of the strongest testing programs in the U.S.

First, public health officials there encourage everyone to get tested for COVID-19 regardless of symptoms or exposure. The state has also prohibited health providers from charging patients for tests. People seeking a test have the option to walk in or to make an appointment ahead of time, whichever is more convenient.

All of this relatively good access to testing has resulted in one of the highest per capita testing rates in the country, at over 20,000 tests per 100,000 people, and a test-positivity rate of around 4%. New Mexico’s testing program is diagnosing a relatively high proportion of cases despite the state experiencing a recent surge.

New Mexico still has room for improvement. Long lines, wait times and limited capacity are becoming more common as cases surge, but the foundation of a strong testing program has helped the state cope with the increase in cases.

 

The big-picture problems

The pre-pandemic infectious disease testing capabilities in the U.S. are clearly unable to meet the current demand. A nationwide response is needed, and there are three things that Congress, the federal government and local governments can do to help ensure COVID-19 tests will be easy to get, fast and accurate.

First, Congress can provide funding to stimulate the testing supply chain, scale up existing testing programs and promote innovation in test development.

Second, governments can improve the management and coordination of testing programs to more efficiently use existing resources.

And third, innovative testing methods that reduce the need for lab capacity – like paper-strip tests and pooled testing – need be approved and implemented more quickly.

Every little improvement in testing capabilities means more COVID-19 cases can be caught before the virus is transmitted. And slowing the spread of the virus is the key to overcoming the pandemic.

 

 

 

 

Test positivity rate: How this one figure explains that the US isn’t doing enough testing yet

Posted on by • Posted in 2020 Election Issues, Asymptomatic Transmission, Clinical Testing, Contact Tracing, Coronavirus, Crisis, Crisis Management, Economic Crisis, Economic Recovery, False Hope, False Narrative, Infection Control, Infection Control Plan, Infectious Virus, Leadership Decentralized, Misinformation, Misinterpret, Mislead, Misleading, Mistake, Mistrust, Mixed Message, Mortality, National Strategy, Pandemic, Positivity Rate - High, Positivity Rate - Low, Public Health, Public Opinion, Public Perception, Public Safety, Public Trust, Quarantine, School Reopening, Scientists, Social Distancing, World Health Organization (WHO) • Leave a comment

https://theconversation.com/test-positivity-rate-how-this-one-figure-explains-that-the-us-isnt-doing-enough-testing-yet-143340

Test positivity rate: How this one figure explains that the US isn ...

The U.S. has performed more coronavirus tests than any other country in the world. Yet, at the same time, the U.S. is notably underperforming in terms of suppressing COVID-19. Confirmed cases – as well as deaths – are surging in many parts of the country. Some people have argued that the increase in cases is solely due to increased testing.

I am a statistician who studies how mathematics and statistics can be used to track diseases. The claim that the increase in cases is only caused by increases in testing is just not true. But how do public health officials know this?

Testing, confirmed cases and total cases

COVID-19 testing has two purposes. The first is to confirm a diagnosis so that medical treatment can be appropriately rendered. The second is to do surveillance for tracking and disease suppression – including finding those who may be asymptomatic or only have mild symptoms – so that individuals and public health officials can take actions to slow the spread of the virus.

At a White House briefing on July 13, the president said, “When you test, you create cases.”

The problem with this statement is that anyone who is infected with the coronavirus is, by definition, a case. Since taking a COVID-19 test does not cause a person to get coronavirus, just like taking a pregnancy test does not cause one to become pregnant, the president’s claim is false. Testing does not create cases.

However, because many COVID-19 cases are asymptomatic, many people are infected and don’t know it. What COVID-19 testing does do is identify unknown cases. And thus it does increase the number of cases that are known, or otherwise called the confirmed case count.

Finding unknown cases is good, not bad, because identifying those who are COVID-19-positive allows individuals and public health officials to take actions that slow the spread of the disease. When public health officials find cases, they can begin contract tracing. When a person finds out they are infected, they will know to quarantine.

Since the beginning of the pandemic, the U.S. has performed more total tests and more tests per capita than any other country, though as of late July the U.K., Russia and Qatar were performing more tests per capita per day. But counting the total number of tests or the tests per capita is not the right way to judge success of a testing program.

As it says on the Johns Hopkins testing comparison page, a country’s “testing program should be scaled to the size of their epidemic, not the size of the population.” Sure, the U.S. might have a big testing program, but it has a massive epidemic. The U.S. needs an equally massive testing program if health officials want to have an accurate picture of what’s really going on.

Test positivity rate

So how do public health officials know if they are doing enough testing?

Better than simply counting total number of tests, the test positivity rate is a useful measure of whether enough tests are being done. The test positivity rate is simply the fraction of tests that come back positive. It is calculated by dividing the number of positive tests by the total number of tests. Generally, a lower test positivity rate is good.

A good way to think about test positivity is to think about fishing with a net. If you catch a fish almost every time you send the net down – high test positivity – that tells you there are probably a lot of fish around that you haven’t caught – there are a lot of undetected cases. On the other hand, if you use a huge net – more testing – and only catch a fish every once in a while – low test positivity – you can be pretty sure that you’ve caught most of the fish in the area.

According to the World Health Organization, before a region can relax restrictions or begin reopening, the test positivity rate from a comprehensive testing program should be at or below 5% for at least 14 days.

There are two ways to lower a test positivity rate: either by decreasing the number of positive tests or by increasing the total number of tests. A comprehensive testing program does both. By conducting a large number of tests, most cases in the community are detected. Then, individual and government actions can be taken that contain the virus. This results in a declining number of positive tests.

Returning to the fishing metaphor, the goal of a comprehensive testing program is to use a huge net to overfish in the coronavirus lake until there are very few COVID-19 cases left. Using the test positivity rate as a measure of success helps ensure that a testing program is appropriately scaled to the size of an epidemic.

As of July 27, the U.S. as a whole had a test positivity rate of 10%. States where testing programs are robust and the virus is fairly well controlled have test positivity rates well below 5%, like Massachusetts at 2.68% and New York at 1.09%. In places like Mississippi and Arizona that are experiencing large outbreaks, test positivity rates are above 20%.

The right amount of testing

The increases in confirmed cases aren’t occurring just because there is more testing. The high test positivity rates in some locations show that the virus is in fact spreading and growing so testing needs to grow with it. I believe that if the U.S. wants to beat back this virus, one of the first things that needs to happen is to increase testing. We need to deploy larger nets to catch more fish. Yes, we’ll find more cases, but that’s the point.