For the estimated 60 million Americans with high blood pressure, frequent blood pressure monitoring can be life-saving.
Video
False readings?
Nov. 7, 2008
Blood pressure is often the first sign of heart attack, stroke, or kidney disease.
"For me, it felt like I wasn't getting enough air, and then I felt dizzy," explains three-time heart attack survivor Tonnette Blair. The 67-year old takes no chances -- checking her blood pressure often.
"I take it twice a day for sure," she says. "Sometimes I take it three times a day."
Blair says her blood pressure hovers around 120 over 70.
As a senior on a fixed income, she often took advantage of the free blood pressure monitors in many grocery stores and pharmacies.
Users push a button - results are clearly displayed in less than a minute.
But are they accurate?
With Tonnette Blair's help, News 8 tested some of those in-store monitors.
Beforehand, she checked her blood pressure -- on her doctor-approved home monitor -- which she uses every day.
We then walked into several stores, randomly, and tried the machines.
What we found is the accuracy fluctuates wildly. A reading at one grocery store was nearly 50 points high.
"167 over 92," read Blair. "That's way off."
Health experts say there are many explanations why these machines might not be the best way to monitor blood pressure.
"Someone with a very large arm or very small arm may get an errant reading," explains Baylor cardiologist Clyde Yancy, "because the cuff may not accommodate the larger size or adjust sufficiently for a smaller size."
Dr. Yancy says making sure the machine is properly calibrated and maintained is also critical.
With a store machine, there's no way to know. Most of the machines are leased to the store. Maintenance records are not publicly posted or provided to store personnel.
News 8 contacted the stores we randomly tested. We were told the machines are simply a public service and not meant to replace traditional monitoring in a doctor's office.
"Almost anything is better than nothing," says Dr. Yancy. "But again, bad information is bad information."
A one-time bad reading doesn't necessarily indicate anything dangerous. But, a false high reading can needlessly cause a patient to panic. Likewise, an incorrectly low number can lull someone into a false sense of security.
A few points higher than normal can make a big difference in the amount of medication Tonnette Blair takes.
"Very much," she says. "So I don't even bother with them now."
Instead, Blair uses that home monitor, which doctors prefer for accuracy, even over a physician's office.
She's taking no chances with her high blood pressure or her health.
