SPRINT: Attended, Unattended BP Measures Do Not Affect Reading or CV Outcomes

Deborah Brauser

November 13, 2017

ANAHEIM, CA — Whether or not staff is in attendance during blood-pressure (BP) measurement techniques appears to have no bearing on the readings—or on CV risk reduction, new research suggests[1].

Further analysis from the seminal Systolic Blood Pressure Intervention Trial (SPRINT), which this time assessed site surveys regarding more than 4000 SPRINT participants, showed similar systolic and diastolic BP levels in those who were alone for a 5-minute rest period and during three BP readings (always alone), those who were alone during just the rest period or just the readings, and those who were never left alone.

In both the always-alone and never-alone groups, those randomly assigned to intensive BP management—defined as 119 to 122 mm Hg at 12 months—had a reduced risk for the primary composite outcome (MI, non-MI acute coronary syndrome, stroke, CHF, or CVD-related death) compared with those who were assigned to standard management (135 to 136 mm Hg).

Although there was no significant reduction in risk for those left alone just during rest or just during readings, those category groups were much smaller, Dr Karen C Johnson (University of Tennessee Health Science Center, Memphis) reported here at the American Heart Association (AHA) 2017 Scientific Sessions.

Dr Karen C Johnson

"Our data suggest that it doesn't really matter if your site staff are in or out of the room when the machine is measuring," Johnson told theheart.org Medscape Cardiology.

"It's much more important to have proper positioning of the patient to allow for a 5-minute rest period and to take multiple measurements and average them," she added.

Asked to comment, former president of the AHA Dr Dan Jones (University of Mississippi Medical Center, Jackson) noted that he was glad to see the investigators delve into these issues.

"Like many people, I was surprised their protocol didn't call for having the absence of a clinician in the room. The fact that they didn't gives us some insight into that blood-pressure measurement," said Jones.

With BP, "there are a lot of variabilities, and it changes moment to moment. Plus, the cuff related to arm size and so forth is a challenge. So it's important that we continue to move forward with research to understand the best way to standardize how blood pressure is measured."

Ongoing Questions, Debates

It's been 2 years since results from the landmark SPRINT trial were first presented at the AHA 2015 Scientific Sessions.

The main findings showed that among 9361 patients, those treated to a SBP target of less than 120 mm Hg had a significantly lower rate of the primary composite outcome than those treated to a SBP target of less than 140 mm Hg (1.65% vs 2.19% per year, respectively; hazard ratio [HR] for intensive treatment 0.75; P<0.001). In addition, the intensive-treatment group had significantly lower all-cause mortality (HR 0.73, P=0.003).

Ever since then, there have been questions, discussions, and ongoing debate about the SPRINT BP goals and how BP was measured.

"Recent publications from investigators not involved with SPRINT have stated that the . . . technique used was unattended, making the BP not comparable with other studies," said Johnson, who is vice chair of the SPRINT steering committee, during a press briefing.

"However, the SPRINT protocol does not address the issue of staff attendance, nor have SPRINT investigators yet published information on this topic," she added.

In the multicenter study, seated BP at every clinic visit was the average of three measurements after a 5-minute rest period. In 99.7% of the cases, a study-provided automated BP-measuring device (Omron 907XL) was used. The participants were asked to refrain from talking or texting during the measurements.

At the end of each visit, site surveys were conducted regarding whether the measurement was attended or unattended by staff. For the current analysis, the investigators assessed data for more than 8600 SPRINT participants.

"We examined whether there were differences in measured clinic BP at baseline and during follow-up and whether there were corresponding differences in SPRINT's major outcome results based on attendance during BP measurement," reported Johnson.

The four categories included the patients who were:

  • Always alone (n=4082 at 38 sites).

  • Never alone (n=2247 at 25 sites).

  • Alone for the resting period (n=1746 at 19 sites).

  • Alone for BP measurement (n=570 at 6 sites).

Look to the Guidelines

The mean systolic BP achieved in the intensive-treatment group in all four categories was 120 mm Hg vs 135 mm Hg for the standard-treatment group. In addition, the intensive group took one more medication than did the standard group.

The HR for the primary outcome for those receiving intensive vs standard treatment in the always-alone group was 0.62 (95% CI 0.51–0.76), and it was 0.64 for the never-alone group (95% CI 0.46–0.91). When the always-alones and never-alones were compared with each other, "there was no evidence of heterogeneity of treatment effect by BP-measurement technique," reported Johnson.

The HRs for total mortality were 0.65 (95% CI 0.47–0.88) and 0.76 (95% CI 0.53–1.11), for the two groups, respectively.

There were no significant differences in the alone-only-for-rest group or the alone-only-for-BP-measurements group for the primary outcome or total mortality.

"I'd say the number one take-away for clinicians is that you should follow the new AHA guidelines on how to take blood pressure, because you're going to get a more accurate reading; and it can help inform your treatment of hypertension," said Johnson.

"I'll add that I get my blood pressure less than 120 and am following the SPRINT guidelines. I'm living it!"

She also recommended the use of automated devices for measuring BP to help in the standardization of care.

"That's very important; and more and more of the practices are going to the automated BP devices. I believe they're more accurate, and you don't have the concern about mercury in the standard sphygmomanometers."

"Somewhat Reassuring"

Official discussant Dr Sripal Bangalore (New York University School of Medicine) said during the press briefing that although it's widely accepted that SPRINT showed that an intensive BP target significantly reduces risk of CV events compared with a standard BP target, exactly what the intensive BP target should be in clinical practice is debatable.

"And a fundamental question post-SPRINT is: were BP measures attended or unattended?"

In this new analysis, Dr Bangalore said that the finding that BP readings were similar across the different measurement groups was "not surprising, since the protocol mandated achieving a BP target."

He also said it wasn't surprising to see similar primary and all-cause mortality outcomes, "since the HR depends on the BP difference between intensive and standard treatment, rather than on the absolute BP values that are the matter of debate."

"More important, the absolute [serious adverse event] rates in the intensive arm were largely similar, which is reassuring but could be confounded by misclassification bias," said Dr Bangalore.

In fact, he noted that the "somewhat-reassuring" results are offset a bit by limitations and unanswered questions, including recall bias and taking center-level data down to patient-level analysis.

Because BP values from manual auscultatory measurement do not equal automated office or ambulatory BP values, "it is not prudent to have the same BP target for different BP-measurement techniques," he concluded.

Blood-Pressure Monitoring "Like Judging Gymnastics"

Session chair Dr Donald Lloyd-Jones (Northwestern University, Chicago, IL) also called the new results reassuring, "but I'd make the important point that this is not the way blood pressure is measured in usual, general-practice settings. It's often this way in hypertension clinics, but not in general practice."

"So, as Dr Bangalore said, it'll be important to translate this information," added Lloyd-Jones.

Jones later told theheart.org Medscape Cardiology that trying to classify a patient's risk factor and cholesterol level "is like running a 100-yard dash and the time is 99.4." However, "blood pressure is more like judging gymnastics," because it's so subjective.

"We need to continue to work to standardize, and I think an automated office blood-pressure [device] is a step in the right direction. We're implementing it in many of our clinics at the University of Mississippi Medical Center. And I think you'll see it more and more," said Jones.

He gave the caveat, though, that a lot more research needs to be done into issues such as if the waiting time is important and whether the room really does need to be vacant of others. "This analysis suggests that that may not be important, but it wasn't randomized. So we still have a lot to learn."

SPRINT was funded by the National Institutes of Health. Johnson reports no relevant financial relationships. Disclosures for the coauthors are listed in the abstract. Jones and Bangalore report no relevant financial relationships.

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