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COVID-19 tests getting more reliable, experts say

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You’re feeling pretty darned sick — headache, fever, fatigue, a cough — but your COVID-19 test came back negative.

What do you do now?

Well, chances are good that you don’t have COVID-19 if that’s what the test says, according to experts.

Labs that are testing for COVID-19 rely on what’s called a PCR test, a slow and complex molecular scan that looks for the genetic material of coronavirus in samples that boasts very high accuracy.

A negative result on this test shows there’s probably something other than COVID-19 wrong with you, said Dr. Bobbi Pritt, chair of clinical microbiology with the Mayo Clinic in Rochester, Minn.

“I know I have several work members and family members who had an influenza-like illness earlier in the year, and it probably was just the common flu or it could have been the common cold,” Pritt said.

Sick folks who test negative for COVID-19 should make sure their doctors also run tests for other infectious diseases, said Dr. Amesh Adalja, a senior scholar with the Johns Hopkins Center for Health Security, in Baltimore.

Tests becoming more accurate

“In general, the tests available are sensitive enough to diagnose those with symptoms accurately, but there are also other infections with similar symptoms that might merit testing for as well,” Adalja said.

PCR tests have improved dramatically during the pandemic, and have also gotten easier to perform.

For example, labs can now get fairly accurate results from gentle nasal swabs or saliva samples, and no longer have to use a long swab to hook a sample from deep within your nasal cavity, Pritt said.

“We can accept nasal swab specimens and even saliva and perform testing on those specimens, and if they are collected correctly the results can be just as good as those that are collected using that gold standard nasopharyngeal swab,” Pritt said.

Labs also are getting results back to doctors more quickly, although they are still struggling to maintain supplies of the chemical reagents they need to perform PCR tests, said Dr. Emily Volk, senior vice president of clinical services at University of Texas Health in San Antonio.

“Turnaround times are improving as more local laboratories and hospitals have been able to bring up the testing,” Volk said. “The more reagents we have available at the local level, the more we’re going to be able to provide turnarounds within 24 hours or less on even the most accurate PCR testing.”

However, there is a chance that you might have gotten a false negative, experts added. The exact accuracy of PCR tests has been tough to pin down. According to Dr. Robert Schmerling reporting in Harvard Health Publishing, “the reported rate of false negatives is as low as 2% and as high as 37%. The reported rate of false positives — that is, a test that says you have the virus when you actually do not — is 5% or lower.”

The timing of when the sample is collected, the type of sample collected and the quality of the sample can all influence the accuracy of the COVID-19 results, said Matthew Binnicker, director of the Clinical Virology Laboratory at the Mayo Clinic in Rochester, Minn.

Test again if needed

“The virus is thought to be present at the highest levels approximately five days, on average, after being exposed, or around the time a person develops symptoms,” Binnicker said. “If a high-quality nasopharyngeal swab is collected within 24 hours of symptom onset, is tested by an approved PCR method and the result is negative, the likelihood of the person having COVID-19 is low,” he explained.

“However, if a less preferred sample — for example, throat swab — is collected after three to five days of symptoms and tested by PCR, a negative result would be less reliable to rule out COVID-19,” Binnicker continued.

If you’re still sick a week after your negative COVID-19 test and you continue to have no idea what’s wrong with you, experts say you should reach out to your doctor for a follow-up coronavirus test.

“If a COVID-19 test is negative, then specific testing for influenza will also need to be performed,” Binnicker said. “If the results are negative for these viruses and the patient continues to be ill, a repeat COVID-19 test can be appropriate. As patients enter into the second week of illness, a lower respiratory sample — like sputum — is preferred over an upper respiratory swab to increase the likelihood of detecting SARS-CoV-2 during the later stages of disease.”

Keep in mind that if you’re sick right now, you probably won’t be given an antigen test, the other form of viral testing for COVID-19 infection.

Antigen tests are cheap and fast, looking for specific structural proteins of the coronavirus that form during infection. The Trump administration made headlines last month by buying out the entire 2020 supply of the just-approved $5 BinaxNOW COVID-19 Ag Card produced by Abbott Laboratories, which the company says will return relatively accurate results within 15 minutes.

Because antigen tests are quick but generally less accurate than PCR tests, they probably will be reserved for screening folks who don’t have any symptoms of possible COVID-19 infection, Pritt said.

“If we are screening large numbers of individuals and we plan on doing that on a regular basis, let’s say college students on a weekly basis, then using an antigen test is probably going to be the best strategy forward because it’s going to be relatively inexpensive and easy to do, and it’s going to be done on a relatively lower risk population,” Pritt said.

More information

The U.S. Centers for Disease Control and Prevention has more about testing for COVID-19.

Copyright 2020 HealthDay. All rights reserved.



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Study: Restricting promotions of sweet foods cuts sugar, not profits

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Limiting marketing of high-sugar foods in supermarkets doesn’t cut into store profits, but it may improve public health, Australian researchers report.

Price promotions, end-of-aisle displays and putting products at eye level can stimulate sales. Ending these practices reduced purchase of sugar-sweetened drinks and candy in participating stores by the equivalent to nearly two tons of sugar, the researchers said. These included foods and drinks with added sugars, as well as natural sugar in honey, syrups and fruit juices.

The reductions in soft drink and candy purchases were particularly large, researchers said. Even so, profits were not affected, they added.

The study, published Oct. 7 in The Lancet Planetary Health, ran for 12 weeks and focused on 20 randomly selected stores in rural Australia. Some stores restricted promotion of sugary foods, others did not.

“Our novel study is the first to show that limiting [promotional] activities can also have an effect on sales, in particular, of unhealthy food and drinks,” said researcher Julie Brimblecombe, an associate professor of nutrition, dietetics and food at Monash University in Melbourne.

“This strategy has important health implications and is an opportunity to improve diets and reduce associated non-communicable diseases. It also offers a way for supermarkets to position themselves as responsible retailers, which could potentially strengthen customers’ loyalty without damaging business performance,” she said in a journal news release.

The changes affected sugar-sweetened drinks, candy and other sweets, table sugar and sweet biscuits or cookies. Among other things, these restricted price promotions, removed end-of-aisle and counter displays, and reduced refrigerator space for sugary drinks while placing large-size soft drinks elsewhere. Stores also promoted water and listed the amount of sugar in soft drinks.

As a result, added sugars purchased in foods and drinks fell 3%. Sugars in purchased sugar-sweetened drinks were cut by 7%, and from soda purchases it dropped 13%. Sugars from candy sales fell 7.5%, the researchers found.

Co-author Emma McMahon, a research fellow at Menzies School of Health Research in Casuarina, Australia, said researchers expected the strategy would work best on impulse items like sweet biscuits rather than on staples like table sugar.

“A different strategy for biscuits and items like table sugar should be explored to stimulate change in those buying behaviors,” she said in the release.

More information

To learn more about sugar and your health, see Harvard University.

Copyright 2020 HealthDay. All rights reserved.



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COVID-19 may have prolonged effect for pregnant women

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COVID-19 symptoms can last a long time in pregnant women, researchers say.

The new study included 594 pregnant women, with average age 31, across the United States who tested positive for the new coronavirus but were not hospitalized. Nearly one-third were health care workers.

On average, the women were about 24 weeks’ pregnant when they joined the study.

The most common early symptoms were cough, at 20%, sore throat, at 16%, body aches, at 12%, and fever, at 12%. By comparison, fever occurs in 43% of hospital patients who are not pregnant.

For 6%, loss of taste or smell was the first symptom. Other symptoms included shortness of breath, runny nose, sneezing, nausea, sore throat, vomiting, diarrhea or dizziness.

While six out of 10 women had no symptoms after four weeks, symptoms lasted eight or more weeks for 25%, the study found.

Thirty-seven days was the median time for symptoms to resolve, meaning half took longer, half took less time. The findings were published this month in the journal Obstetrics and Gynecology.

“COVID-19 symptoms during pregnancy can last a long time, and have a significant impact on health and well-being,” said senior author Dr. Vanessa Jacoby. She is vice chairwoman of research in the department of obstetrics, gynecology and reproductive sciences at the University of California, San Francisco.

Jacoby’s team also found that COVID-related symptoms were complicated by overlapping signs of normal pregnancy, including nausea, fatigue and congestion.

The majority of participants had mild disease and were not hospitalized, said first author Dr. Yalda Afshar, assistant professor in the division of maternal fetal medicine, department of obstetrics and gynecology at the University of California, Los Angeles.

Despite the potential risks of COVID-19 for pregnant women and their newborns, large gaps in knowledge about the disease’s course and prognosis remain, Afshar noted in a UCSF news release.

“Our results can help pregnant people and their clinicians better understand what to expect with COVID-19 infection,” Afshar said.

More information

There’s more on COVID-19 and pregnancy at the U.S. Centers for Disease Control and Prevention.

Copyright 2020 HealthDay. All rights reserved.



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Pregnant women with COVID-19 don’t pass the virus to their newborns, study finds

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Oct. 12 (UPI) — New mothers infected with COVID-19 during pregnancy didn’t pass the virus to their babies, even if they breastfed and shared the same hospital room, according to a study published Monday by JAMA Pediatrics.

Mothers with severe COVID-19, however, delivered their babies, on average, one week earlier than healthy mothers, and their babies were four times as likely to need phototherapy to treat jaundice, the data showed.

“Between our findings and other studies, it is now known that there is a relatively low likelihood of vertical transmission from [COVID-19]-positive mothers to their newborns,” study co-author and pediatrician Melissa Stockwell told UPI.

“We also show that the risk remains low even with newborns rooming-in and direct breastfeeding practices, both of which had been concerns early in the pandemic,” said Stockwell, division chief of child and adolescent health at NewYork-Presbyterian/Columbia University Irving Medical Center.

Pregnant women may be at increased risk for severe illness from COVID-19, and reports have appeared that the risk for preterm delivery is higher among women infected with the virus, according to data released in June by the U.S. Centers for Disease Control and Prevention.

“There remains a concern for the effect of this virus on pregnant women,” study co-author Dr. Cynthia Gyamfi-Bannerman, a maternal-fetal medicine specialist at NewYork Presbyterian, told UPI.

However, no indication exists — at least to date — that their newborns are at any risk from the virus.

To explore the issue further, the Columbia University researchers tested 101 babies born to infected mothers in New York City between March 13 and April 24 — the height of the COVID-19 outbreak in the region.

Two of the babes had low levels of the virus in their nasal and throat samples initially, but neither developed symptoms, and they later tested negative, the researchers said.

The remainder all tested negative at birth and, and the 31 infants who were retested several days later remained negative. All 101 babies “roomed in” — or shared the same hospital rooms as their mothers — and bathing was delayed, the researchers said.

Some studies have recommended early bathing of babies born to mothers with COVID-19 as a way to reduce risk for virus spread, but early bathing has other health risks, including hypothermia, they said.

Three of the 10 babies born to mothers with severe COVID-19, however, required phototherapy, while six of 91 born to mothers with mild to moderate disease required the treatment, the data showed.

“Treating babies as babies seems safe during the COVID-19 pandemic,” study co-author Dr. Dani Dumitriu told UPI.

“This is particularly important given the continued spread of COVID-19 throughout the country and around the world,” said Dumitriu, a neonatologist at New York-Presbyterian.



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