SECOND OPINION | Home blood pressure readings are off the mark, and a sex guide for scientists
Hello and happy Saturday! Here’s our roundup of the week’s interesting and eclectic news in health and medical science.
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Home blood pressure monitors not accurate: U of Alberta study
When University of Alberta researchers tested the accuracy of home blood pressure monitors, they were surprised at how often the readings were wrong.
“It’s a big issue and it’s a widely ignored.” Dr. Raj Padwal told CBC News. “High blood pressure is the number one cause of death and disability in the world. One quarter of Canadians have it. We need accurate measurements.”
One potential problem with the home units is that they’re tested on healthy people, Padwal said. “I’m really concerned that it’s not as accurate in people who have vascular stiffness and diseases.”
When Padwal and his team used the home machines to do a series of tests with volunteers, many with hypertension, the readings were off almost 70 per cent of the time.
Blood pressure is measured in “millimeters of mercury” (mmHg). Ideally the devices should take measurements that are within 5 mmHg of the gold standard. But the study revealed that two thirds of the machines took measurements that were off by more than 5 mmHg, a difference considered to be clinically important.
“That could be the difference between starting or stopping a drug,” Padwal told us.
The machines use a technique called “oscillometry,” analyzing waveforms to derive a blood pressure estimate. The traditional method of listening with a stethoscope is called auscultation. It’s technically more accurate. However those readings are also frequently flawed because of human error and white coat syndrome — where the patient becomes anxious at the sight of the doctor.
“I wouldn’t quit doing home monitoring but I would ask people to do a lot of readings,” Padwal said. He asks his patients to take two readings in the morning and two in the evening for seven days and then he averages out the results. “I still trust that more than readings we get in the clinic,” he said.
Still, he’s frustrated that the industry has not come up with better systems, perhaps using electronic stethoscopes.
“I’m surprised there’s not more being done in the field of electronic listening,” he said. “In the interest of accuracy, we really should look at an electronic stethoscope because that might in the end be a better device. They were invented decades ago but the industry went in a different direction and nobody looked back.”
‘In the interest of accuracy, we really should look at an electronic stethoscope because that might in the end be a better device.’ – Dr. Raj Padwal
When doctors use the stethoscope method, they inflate the cuff around the arm, closing off the blood vessel. Then as they slowly release the pressure, they listen for what are called “Korotkoff sounds,” which Padwal describes as a series of knocking noises as blood spurts into the artery.
“Essentially what you’re trying to determine is when the knocking sounds start and when the knocking sounds end. And those two parameters correspond to systolic and diastolic blood pressure.”
To hear what the doctor hears through the stethoscope, listen here, courtesy of Thinklabs Medical.
Show us your data
A major controversy is raging in the scientific community over the question of whether researchers should be forced to share their clinical trial data with other scientists.
This week an influential group of journal editors announced a new-data sharing policy that will take effect next year. To get published in the top journals, scientists will have to include a plan for sharing data.
But the editors stopped short of making data sharing completely mandatory, to the disappointment of some who argue it’s important for trial data be opened up to allow independent scientists to reproduce the research.
The new policy from the International Committee of Medical Journal Editors (ICMJE) is a tentative first step in a process that triggered heated protests from scientists when the deliberations began a year ago. Concerns ranged from privacy issues, to technical problems of sharing data.
The World Health Organization and other groups have called for greater transparency in clinical trial research, including the requirement to publish all data, to register all trials, and to share data when requested.
Quebec finally screening for CF
Until this week, Quebec was the only jurisdiction in North America not screening newborns for cystic fibrosis, an inherited disease that requires intensive treatment and often leads to premature death.
But on Thursday the Quebec government finally agreed to the long standing demand from doctors and families. Cystic Fibrosis Canada said it was overjoyed at the news.
The disease can be quickly and easily diagnosed in newborns using a blood test. That means intervention can begin immediately.
Dr. Larry Lands, professor of pediatrics at McGill University, discovered that children diagnosed through newborn screening in Alberta and Ontario “grew better, were less often hospitalized, and had fewer lung infections” than children in Quebec who were only diagnosed after symptoms appeared.
At this point there is no cure for the genetic disease, which affects one out of 3,500 babies born in Canada. But early disease management can reduce lung damage and improve growth. That’s why groups have been lobbying Quebec for 15 years to start CF screening.
What took so long? It’s a question no one seemed to be able to answer. We asked the Quebec Health Ministry and received no response. Some speculated that it might have been concerns about funding. The screening will cost Quebec about $5.00 per child or about $350,000 per year.
Dr. Lands says early diagnosis is more important than ever, now that investigational drugs are showing promise at correcting the cellular defect and slowing progression of the disease.
A sex guide for scientists
Dr. Franck Mauvais-Jarvis is still amazed at how blind biologists are to sex.
So, the physician scientist at Tulane University in Louisiana has decided to spell it out for them in how-to guide for studying sex differences on metabolism.
Rule number one: don’t assume the male is representative of the species. Dr. Mauvais-Jarvis says many scientists still make that mistake, which means most mechanisms of disease are studied in male animals, or male cells.
- Sexist assumptions about lab mice lead to skewed drug research
- Women’s period seen as barrier to medical research
“Even the best scientists, when you ask them ‘have you considered sex,’ they say ‘I prefer to study the mechanism first.’ But sex is part of the mechanism.”
“It’s not just a story of hormones. It’s more complicated than that,” he told us. Male and female creatures need to be studied as two separate biological systems.
As proof, he points to recent FDA warnings about drugs that affect women differently than men.
By failing to concentrate on sex-specific variables, he says scientists could be missing an important opportunity for discovery. That’s because some major diseases affect men and women differently, including Alzheimer’s disease and auto-immune disorders. It suggests that one sex is protected in some way.
“If you can understand why and how biologically it is protected, if you can harness that difference you have a therapeutic avenue to pursue. It’s so simple, but many people have not thought about that.”
Research programs are scrambling to make up for lost time. Increasingly scientific granting agencies, including the Canadian Institutes for Health Research, are demanding that researchers and reviewers consider sex as a variable when designing studies.
Ontario onions kill cancer? Put them on the list
“Red Onions Pack a Cancer-Fighting Punch, Study Reveals.” That news flashed in our email boxes this week from the press office at the University of Guelph, reporting results from a study on five varieties of Ontario-grown onions.
Our health unit colleague Vik Adhopia thought the headline sounded familiar. So he plugged it into a Google search —minus the phrase “red onions” — and watched in amazement as a parade of other fruits and vegetables appeared making the same claim.
Tomatoes, pomegranates, peaches, green tea, broccoli, purple potatoes, horseradish and blueberries are among the fruits and vegetables also professing to pack a cancer-fighting punch.
McGill University professor Joe Schwarcz has written many books debunking health claims like this. We asked for his opinion.
“I looked at the papers and the press release. There is really nothing new here,” he told us.
The Guelph researchers isolated a onion flavonoid called quercetin and tested it against breast and colon cancer cells to see how it performed compared to other flavonoids.
But putting an onion extract into a Petri dish with some cancer cells and seeing an effect is not that surprising, Schwarcz said.
“The fact that there is an effect on cancer cell multiplication in vitro doesn’t mean much. There are hundreds of fruit or vegetable extracts or purified antioxidants that do this. So will sulphuric acid or Drano.”
But he says there is no evidence that eating a specific food will fight cancer in the body.
“What we do know is that a diet that features lots of fruits and vegetables is desirable but suggesting that specific ones should be sought out is not scientifically justified.”
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