Tag Archives: rapid Covid testing

The Covid testing dilemma

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England’s pushing mass testing as a way to contain Covid. It’s free, it’s government approved, it’s somewhere between uncomfortable and painful, and it may or may not be a good idea. Let’s tear the numbers apart and see what we can figure out.

Since the schools reopened, secondary students–those are the older kids–have had to do quick Covid tests twice a week, and that’s been a bulwark of the program to keep the schools open while not letting the virus get out of control. 

The tests, unfortunately, have a reputation for being unreliable, especially when done by non-experts. Since the kids are doing their own tests, or asking their parents or three-year-old sisters to stick the swabs up their noses and down their throats, these are in the hands of the distilled essence of non-expert. One fear about relying on the quick tests has been that false positives will send a lot of people into isolation unnecessarily. So half of the positive tests were sent to a lab to be confirmed by the slower, more reliable tests, and only 18% of them were false positives. 

Irrelevant photo: Rhododendrons. Photo by Ida Swearingen

But wait, because we’re not done yet. Those numbers are from March, and Covid rates have fallen, at least in parts of the country. (Some hot spots remain, and I don’t know if numbers are falling there as well. Just put that possibility off to one side. The recipe may call for it later. If it doesn’t, we’ll stick it in the freezer.) The point is that where the number of cases is lower, everything changes. 

Why? Because the tests will crank out the same number of false positives, no matter how many people are infected. Find yourself a population of people who’ve never been exposed to Covid and the test will swear on any religious book you like that some of them are infected. 

I’m about to throw some numbers at you, so if your allergies are bad today just skip a few paragraphs.

Ready? In London, the southwest, the northeast, and the southeast of England, the prevalence of Covid ranged from 0. 08 to 0.02. In England as a whole, it was 0.12%. Using those figures (I’d assume that means the England-wide ones), it would take 16,000 tests to find one infected person. If the tests cost £10 each, that means spending £160,000 to find that one person.

Is that worth it? If we were trying to stamp the disease out and keep it stamped, as New Zealand is, it would be. Given that we treat stamping it out as the silly thought of irresponsible day dreamers, probably not. 

Meanwhile, in leaked emails (I do l love a good leak) “senior government officials” are talking about scaling back mass testing, although the Department of Health and Social Care says it has no plans to end the program. One in three infected people, they remind us, show no symptoms but is still contagious. 

That brings us neatly to the question of whether the rapid tests will spot that one person. In other words, it’s time to talk about false negatives. Administered by an expert, the tests pick up 79% of infections. Or to put that the other way around, they miss 21%, and those are mostly people with a low viral load. Or to put that another way, they’re most likely to miss people who don’t have symptoms, who are just the people the testing program is looking for.

Administered by secondary school students or their three-year-old sisters, they’re more likely to pick up 58% of infections, or to miss–umm– I think that’s 42%. Although estimates of the number of cases the test misses vary. It might be as high as 50%. 

The government denies that it has any plans to scale back anything ever and Boris Johnson is urging everyone to get tested twice a week. Even though his advisors say that in areas with low infection rates, only 2% to 10% of the positive results may be accurate. 

But what the hell, guys, we’ve got these tests. Someone’s cousin has the contract for them. Use them, will you, please? For the good of the nation.

 

News of an accurate rapid test that’s in development

A new test is being developed that’s both fast and accurate. It also tracks variants and tests for other viruses that might be mistaken for Covid. It can screen 96 samples at a time and within 15 minutes it starts to report the samples as negative or positive. In 3 hours, it will have sequenced all its samples. 

It’s also small and portable. It doesn’t make coffee, but it just might be able to make you a cup of tea.

Juan Carlos Izpisua Belmonte, a professor in Salk’s Gene Expression Laboratory where it’s being developed, said, “We can accomplish with one portable test the same thing that others are using two or three different tests, with different machines, to do.”

That’s the good news. But will it go from development to being manufactured and used?

“Market analysis would be required to determine whether the initial cost of commercialization—and the constant tweaks to the test needed to make sure it detected new variants or new viruses of interest—are worth it.”

I believe that translates to “maybe.”

It’s called NIRVANA, which doesn’t seem to stand for anything, so I don’t know why it’s in all caps. 

 

High- and low-tech approaches to Covid

In New Zealand, they’re trying out an app that connects to smart watches and fitness trackers, monitoring people’s heart rate and temperature. It’s called an Elarm and the developer claims it can spot 90% of Covid cases up to three days before symptoms appear.

Does that include people who don’t go on to develop symptoms? I’m have to give you a definite maybe on that, because the article I found doesn’t address it. The company’s own website doesn’t answer the question either but says it will also let you know about stress and anxiety, although you might notice those without needing an app. Basically, it figures out your normal levels and lets you know when you’ve wandered off them, so you could end up going into isolation over the flu as easily as over Covid. That would scare the pants off you but would, at least, take a lot of the punch out of flu season.

So how do you use this? New Zealand wants its border force to try it out, since almost the only cases of Covid there are in incoming travelers, who have to go into quarantine, meaning the people who work for the border force are in the front lines.

When New Zealand says quarantine, by the way, they actually mean quarantine. It’s one reason they’ve been able to contain the virus.

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On the other end of the scale comes the recommendation that we open windows in public places to minimize Covid transmission. It’s cheap, it’s simple, and–

Oh, hell, how many public places these days have windows that open? Okay, ventilation. The air in public indoor spaces needs to be replaced or cleaned. 

We’ve heard a lot about keeping two meters (or yards) away from people to avoid contagion, but in addition to the heavier droplets people breathe out, which can carry Covid, the tiniest particles that we breathe out can also carry it, and they can stay suspended in the air for hours. The goal is to run them outside and get some fresh air in. 

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If you’re looking for a low-tech way to decide how far from people you should be standing, you can think of it this way: If you can smell that they’ve had garlic or peanut butter for lunch, you’re too close. 

 

Drug news

An asthma drug, budesonide, has been shown to shorten people’s Covid recovery time –and it can be used at home without anyone involved needing welding gloves, a deep-sea diver’s helmet, or a set of allen wrenches. It’s relatively inexpensive and comes in an inhaler. It shortened people’s recovery time by three days and at the end of two weeks the people who used it were in better shape than the control group.

It’s not clear yet whether it made hospitalization less likely. In the budesonide group, 8.5% were hospitalized. In the control group, that was 10.3%. That sounds like a result, but the problem with interpreting the numbers is that hospitalization rates are dropping in Britain. If you want to understand why that makes the numbers hard to interpret, you need to talk to someone who actually knows something.

Everyone in the test was over 50 and had underlying health problems. The drug can be used in the early stages of infection. 

Does the Covid virus work nights? It’s the pandemic update from Britain

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With Covid cases rising in Britain and more than a quarter of the country living with local restrictions on top of the national ones, pubs in England have been told to close at 10 pm. So who can resist a story about Parliament’s bars being exempt from the rules?

Parliament has thirty bars and the booze is subsidized, so it’s cheap. And we shouldn’t be calling it booze, because a lot of these people are high-class guzzlers. They’re not in the habit of letting people talk about them as if they were your everyday, low-rent lush. They are extremely high-rent lushes.

But high rent or not, sitting in the House of Commons or the House of Lords is a thirsty job, so they need those bars. Which, I assume, is why they were neatly defined as workplace canteens, which gave them an exemption on both hours and a few other things until the opposition–that’s the Labour Party–started yelling, the whole thing got a bit of embarrassing publicity, and someone decided that, gee whiz, guys, this might give people the wrong idea about us. 

The bars now stop serving at 10 pm, and that will last until either the regulations change or outsiders promise not to notice.

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Irrelevant photo: Pansies. I’ve given up growing them. The slugs and snails just love ’em.

What’s the logic behind closing the bars at 10 pm? According to our prime minister, who’ll say anything that comes into his head, however incoherent it may be, “What we’ve seen from the evidence is that the spread of the disease does tend to happen later at night after more alcohol has been consumed.” 

What evidence do they have that the disease spreads late at night once the viruses or their containers (that’s us) have gotten shitfaced? Well, the BBC asked the Department for Health and Social Care for the specific evidence and didn’t get it. Instead, the BBC ran through an assortment of data from Public Health England, showing the number of outbreaks in schools, food-related businesses (you can slot the pubs in there), care homes, and workplaces, but it inevitably showed more transmission in places where testing’s heaviest, so it’s anything but conclusive. And it doesn’t mention time of day. Or night. 

Professor Mark Woolhouse, who’s on the government’s infection modelling team, explained (helpfully), “There isn’t a proven scientific basis for any of this.”

So as far as we know, the virus works both the day shift and the night shift.

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A study has begun on how long Covid can survive once it’s airborne. Figure that out and  you can figure out how to reduce the risk people run in enclosed spaces. 

The consensus is that it’s not just the larger droplets that humans breathe, cough, and sneeze out that carry the disease, it’s also aerosols–tiny beasties less than  5 microns across, which hang in the air much longer than droplets. By way of comparison, a human hair is 60 to 120 microns across. 

Because aerosols are so small, they stay airborne longer than droplets and can be carried by air currents. 

Humans are messy creatures, always breathing–not just in but (annoyingly) out–and we tend to share whatever’s taken up residence inside us. So if the disease does spread on aerosols, keeping two meters away isn’t going to keep us safe. 

Earlier research gave the rough estimate that Covid has a half-life of 1.1 to 1.2 hours in aerosol form, but the new research will create a closer replica of real-world conditions, even varying it for different climates. I’m hoping they don’t tell us that we all need separate countries. In spite of how difficult we are as a species, I actually like being around other humans. Not all of them, but a fair few.

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Here’s a quick snapshot of Britain at the moment: University students across the country went back to school this month, and (to no one’s surprise) universities are reporting Covid outbreaks. They’re being urged in all directions: to drop all face-to-face teaching, to continue normal teaching, to be sure campuses are two-thirds empty, to quarantine affected students and pretend that in a dorm that solves the problem, to let student life carry on as usual because the climate of fear is doing untold damage, to return the tuition they charged, and to keep the tuition they charged.  

The only way to choose the correct advice is by having a gorilla throw darts at a target.

A report says infections in the food industry are thirty times higher than are being reported. 

A scientist from SAGE–the group of scientists who advise the government–is arguing that repeated two-week lockdowns could knock the virus on the head. Not necessarily hard enough to kill it but enough to make it dizzy.

Outside of Britain? The world has now logged a million coronavirus deaths. Those are the ones that’ve been counted. How many are there really? No one knows. Countries haven’t even agreed on the definition of a coronavirus death, and we won’t get into the problem of figuring out who actually had it when testing is so patchy. But basically, a lot of people have died, and that’s not taking account of the people who are left debilitated or of the economic damage the pandemic leaves in its wake.

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A quick Covid test is now available. It gives a result in 15 to 30 minutes and works like a pregnancy test, but nine months later you don’t have to wake up in the middle of the night and feed anybody. 

Unless of course you want to. 

The makers claim it’s 97% accurate, but in real-world conditions it picks up something more like 80% to 90% of infections. Other quick tests are sold online, but this is the first one that meets the World Health Organization’s standards. By way of illustration, Spain ordered two sets of rapid tests in March and sent them back.

A second test is expected to get WHO approval shortly.

Under an initiative started by the WHO, the European Commission, the Gates Foundation, and the French government, 20% of the tests will be made available to low- and middle-income countries for $5 per test. The rest will go to wealthy countries. You may notice an, um, imbalance there between what wealthy countries get and what poor ones do, but it’s actually better than the alternative, which is to have them all go to the countries that can pay the most. 

Yes, it’s a lovely world we live in.

Right now, most low- and middle-income countries are doing minimal testing. North America tests 395 people per 100,000 daily, Europe tests 243, and Africa tests fewer than 16, but most of those are in just three countries, Morocco, Kenya, and Senegal.

It’s not clear whether the UK plans to buy any of the tests. It’s committed heavily to two different tests that take 90 minutes, aren’t as easy to use, and cost more.

 

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A reporter asked Boris Johnson to explain the tighter local restrictions that northeastern England is living with and, to prove how simple the rule of six is, he got it wrong. It all has to do with how many people you can get together with indoor and outdoors.

Here’s how it really works:

If you’re outside the restricted area, it’s six inside and six outside. But if you’re inside, it’s six inside but not six outside. 

I hope that clears everything up. If not, just hide in your basement, knock the glass out of a periscope, and breathe through that. We’ll look for you when this all passes, as all things must.