Are Your Blood Pressure Readings Accurate? New Study Sows Doubt

Measuring a patient’s blood pressure is a routine task that every nurse knows like the back of their hand, but a new study suggests these readings aren’t always accurate. Blood pressure readings taken in the office may be much higher than when taken at home. It’s a small change that’s affecting millions of Americans all over the country.

Why Blood Pressure Readings Aren’t Always as They Appear

The American College of Cardiology, the CDC, and other medical organizations say that a normal blood pressure reading should be below 120 over 80 mmHg. As you probably know, there’s a right way and a wrong way to take a person’s blood pressure.

The American Heart Association (AHA) has clear guidelines, including that the cuff should be placed over the bare skin, the patient shouldn’t be talking, the arm should be supported with the elbow at the forearm’s level, back supported, legs uncrossed, and both feet flat on the floor.

High blood pressure is a leading risk factor for heart attack and stroke. The CDC says about 45% of Americans have high blood pressure, and just 24% of them have it under control. In 2018, hypertension caused or contributed to around a half-million deaths in the U.S.

That’s why it’s so important for Americans to keep an eye on their blood pressure, whether they’re measuring it by themselves at home or having a nurse do it at the office.

The new study from the Systolic Blood Pressure Intervention Trial (SPRINT) shows that blood pressure readings taken during routine clinic appointments were consistently higher than those taken during the study’s trial, which carefully adhered to AHA guidelines.

That’s not all.

In 2015, the U.S. Preventive Services Task Force, an independent body of medical experts that studies disease prevention and evidence-based medicine, found that 15% to 30% of people with high blood pressure readings at routine clinic appointments may have lower readings outside of that setting.

The “White Coat Syndrome”

Medical experts say there may be several reasons for all these inaccuracies. Many patients may experience what’s known as the “white coat syndrome”, which marks a change in BP readings when the patient is in the presence of a medical professional.

They suggest some patients may have rushed to get to their appointment, navigating parking, subways, and public transportation, leading to a spike in BP readings.

Despite these variations, experts say it’s clear that many clinics and providers aren’t following the AHA guidelines.

Kevin Hwang, an associate professor of general internal medicine at McGovern Medical School at the University of Texas, has been studying these inaccuracies and getting an earful from patients.

“I’ve had a lot of patients come to me and they will say, ‘Hey, one reason I wanted to talk with you is because I got my blood pressure measured and they said it was 160 over 100, but I had no previous symptoms,’” Hwang explains.

“A lot of times, they will say, it was in a dentist’s office, they were lying back in a dentist’s chair or it was done in a pharmacy where they didn’t rest, and their back was unsupported. By the time they are seen in our office, it’s 20-30 points lower.”

Hwang said around 50% of patients reported lower BP readings at home compared to clinical settings. “It’s a mixed bag when you look at research, depending on the thickness of the sleeve, age of patient and other factors,” he said. “For example, it may not make a difference in young patients but does so in older patients.”

Paul Whelton, Show Chwan professor of global public health at Tulane University’s School of Public and Tropical Medicine, says these inaccuracies can have serious implications when it comes to preventing stroke and heart attack.

“It leads to a lot of error, and most of the time, the error is going to be an overestimation of the true average blood pressure, but sometimes it’s underestimation and there’s no way to deal with that,” Whelton said.

He suggests medical providers with more time on their hands than nurses, such as technicians and medical assistants, should be trained to record the patient’s blood pressure. “Usually people who are pretty busy don’t take the time,” he said.

Ray Thomas, 67, is one of the many Americans that fears going to the doctor’s office. He says he can feel his heart beating out of his chest when he goes in for an appointment. To ensure his BP readings stay accurate, he now asks the nurses on staff for some time to rest before they measure his blood pressure.