HEALTH

Weekender

Are coronavirus tests flawed?

THERE are deep concerns laboratory tests are incorrectly telling people they are free of the coronavirus.
Stories in several countries suggest people are having up to six negative results before finally being diagnosed.
Meanwhile, officials in the epicentre of the epidemic, Hubei province, China, have started counting people with symptoms rather than using the tests for final confirmation.
As a result, nearly 15,000 new cases were reported on a single day – a quarter of all cases in this epidemic.
What are these tests and is there a problem with them?
They work by looking for the genetic code of the virus.
A sample is taken from the patient. Then, in the laboratory, the virus’s genetic code (if it’s there) is extracted and repeatedly copied, making tiny quantities vast and detectable.
These “RT-PCR” tests, widely used in medicine to diagnose viruses such as HIV and influenza, are normally highly reliable.
“They are very robust tests generally, with a low false-positive and a low false-negative rate,” Dr Nathalie MacDermott, of King’s College London, says.
But are things going wrong?
A study in the journal Radiology showed five out of 167 patients tested negative for the disease despite lung scans showing they were ill. They then tested positive for the virus at a later date.
And there are numerous anecdotal accounts.
These include that of Dr Li Wenliang, who first raised concerns about the disease and has been hailed as a hero in China after dying from it.
He said his test results had come back negative on multiple occasions before he had finally been diagnosed.
Chinese journalists have uncovered other cases of people testing negative six times before a seventh test confirmed they had the disease.
And similar issues have been raised in other affected countries, including Singapore and Thailand.
In the US, meanwhile, Dr Nancy Messonnier, of the the Centers for Disease Control and Prevention, says some of its tests are producing “inconclusive” results.
What might be going on?
One possible explanation is the tests are accurate and the patients do not have coronavirus at the time of testing
It is also cough, cold and flu season in China and patients may confuse these illnesses for coronavirus.
“The early signs of coronavirus are very similar to other respiratory viruses,” Dr MacDermott says.
“Maybe they weren’t infected when first tested.
“Then, over the course of time, they became infected and later tested positive for the coronavirus. That’s a possibility.”
Another option is the patients do have the coronavirus but it is at such an early stage, there is not enough to detect.
Even though RT-PCR tests massively expand the amount of genetic material, they need something to work from.
“But that doesn’t make sense after six tests,” Dr MacDermott says.
“With Ebola, we always waited 72 hours after a negative result to give the virus time.”
Alternatively, there could be a problem with the way the tests are being conducted.
There are throat swabs and then there are throat swabs.
“Is it a dangle or a good rub?” asks Dr MacDermott.
And if the samples are not correctly stored and handled, the test may not work.
There has also been some discussion about whether doctors testing the back of the throat are looking in the wrong place.
This is a deep lung infection rather one in the nose and throat.
However, if a patient is coughing, then some virus should be being brought up to detect.
A final option is the RT-PCR test for the new coronavirus is based on flawed science.
In order to develop the test, researchers must first pick a section of the virus’s genetic code.
This is known as the primer. It binds with the matching code in the virus and helps bulk it up. Scientists try to pick a region of the virus’s code they do not think will mutate.
But if there is a poor match between the primer and the virus in the patient, then an infected patient could get a negative result.
At this stage, it is impossible to tell exactly what is going on so lessons for other countries are unclear.
“It is not going to change that much,” Dr MacDermott says.
“But it flags up that you have to test people again if they continue to have symptoms.” -BBC


Waist size may be more important than weight

HEART attack survivors who carry extra weight around their belly are at greater risk of another heart attack, new research has found, another reason why measuring your waist may be more important than stepping on the scale.
It’s been known for a while that having a pot belly, even if you are slim elsewhere, increases the odds of having a first heart attack, but the latest study, which published Monday in the European Journal of Preventative Cardiology, is the first time researchers have found a link between belly fat and the risk of a subsequent heart attack or stroke.
The link was particularly strong in men, researchers said.
“Abdominal obesity not only increases your risk for a first heart attack or stroke, but also the risk for recurrent events after the first misfortune,” said Dr. Hanieh Mohammadi of the Karolinska Institute in Stockholm, in a news release.
“Maintaining a healthy waist circumference is important for preventing future heart attacks and strokes regardless of how many drugs you may be taking or how healthy your blood tests are.”
The study tracked more than 22,000 Swedish patients after their first heart attack and looked at the link between their waist circumference and events caused by clogged arteries like fatal and non-fatal heart attacks and stroke. Patients were followed for nearly four years, with 1,232 men (7.3 per cent) and 469 women (7.9 per cent) experiencing a heart attack or stroke.
Most patients — 78 per cent of men and 90 per cent of women — had abdominal obesity, defined as a waist circumference of 94 cm (37.6 inches) or above for men, and 80 cm (32 inches) or above for women.
The study found that belly fat was associated with heart attacks and stroke independent of other risk factors like smoking, diabetes, hypertension, body mass index and prevention treatments. The researchers stressed that waist circumference was a more important marker than overall obesity and advised doctors to measure their patient’s waists to identify those at risk.
However, they said that the link was stronger and more linear in men, who made up nearly three-fourths of the patients included in the study, than women.
In women, Mohammadi said the relationship was “U-shaped” rather than linear, meaning that the mid-range waist measurement, rather than the narrowest, was least risky. What’s more, the mid-range waist measurement was in the range traditionally recognized as at risk for abdominal obesity: more than 80 cm wide.
The reason for this could be down to the type of fat that tends to hang out on men’s and women’s bellies. Mohammadi said some studies have suggested that men may have more visceral fat that goes deep inside your body and wraps around your vital organs.
This fat can be turned into cholesterol that can start collecting along and hardening your arteries, perhaps ultimately leading to a heart attack or stroke.
“In women it is thought that a greater portion of the abdominal fat is constituted by subcutaneous fat which is relatively harmless,” she said.
However, the lower numbers of women included in the study meant the findings had less “statistical power” and more research was needed to draw definite conclusions, Mohammadi said.
The risk of cardiovascular disease like heart attacks or strokes is considered to be higher in those with a waist measurement of above 94 cm in men and above 80 cm in women, according to the World Health Organization. The risk is thought to be substantially increased in men with a waist wider than 102 cm and 88 cm in women.
The authors said that belly fat was best tackled by a healthy diet and regular exercise. Earlier studies have shown that regular moderate cardio, like walking for at least 30 minutes a day, can help fight a widening waistline. Strength training with weights may also help but spot exercises like sit-ups that can tighten abs won’t touch visceral fat. – CNN

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