Results Summary
What was the research about?
Because high blood pressure has no symptoms, a correct diagnosis is important for getting treatment to prevent strokes, heart attacks, or other future health problems. To diagnose high blood pressure, medical guidelines recommend wearing a monitor at home that checks patients’ blood pressure over 24 hours. But doctors rarely suggest this approach.
In this study, the research team wanted to learn if other methods to check blood pressure worked as well as the 24-hour monitor to diagnose high blood pressure. The team compared the 24-hour monitor with three methods:
- Clinic. Patients returned to the clinic once and staff checked their blood pressure.
- Home. For five days, patients took their blood pressure at home, twice in the morning and twice at night.
- Kiosk. For three days, patients took their blood pressure three times, a minute apart, at a kiosk in a clinic or pharmacy.
The research team also looked at patient health outcomes after six months.
What were the results?
Overall, the home method had the best results:
- The home and kiosk methods had more accurate readings than the clinic method. The clinic method missed high blood pressure more than half of the time.
- At home, more patients checked their blood pressure as planned than at the clinic or kiosk.
- Patients preferred checking their blood pressure at home to the clinic or kiosk.
After six months, across the three methods, patients had lower blood pressure. Patients didn’t differ in how much their blood pressure went down, changes in their physical health, or whether they made lifestyle changes like eating less salt.
Among patients with high blood pressure according to the 24-hour monitor, only 40 percent had the diagnosis recorded in their health record six months later.
Who was in the study?
The study included 510 patients receiving care at one of 12 clinics in Washington State. Among patients, 80 percent were White, 7 percent were African American, 13 percent were another race, and 4 percent were Hispanic. The average age was 59, and 52 percent were men.
What did the research team do?
The research team identified patients who had high blood pressure at their last clinic visit based on health records. They enrolled patients who still had high blood pressure at the first study visit and assigned them by chance to one of the three methods. After three weeks, patients wore the 24-hour monitor. The team compared the results from each method with the results from the 24-hour monitor.
Patients completed surveys at the start of the study, before and after wearing the 24-hour monitor, and six months later.
Patients, doctors, and other experts in measuring blood pressure helped design the study.
What were the limits of the study?
The study took place in one healthcare organization. Most patients were White. Results may differ for other patients.
Future research could test ways to increase use of the home method to diagnose high blood pressure.
How can people use the results?
Health systems and doctors can use the results when considering ways to diagnose high blood pressure.
Professional Abstract
Objective
To compare the effectiveness of three blood pressure (BP) monitoring methods—clinic, home, and kiosk—versus 24-hour ambulatory BP monitoring (ABPM) in diagnosing hypertension
Study Design
| Design Element | Description |
|---|---|
| Design | Randomized controlled trial |
| Population | 510 adults ages 18–85 with elevated BP, without a previous diagnosis of hypertension and not taking hypertension medication |
| Interventions/ Comparators |
|
| Outcomes |
Primary: difference in mean systolic and diastolic BP between each BP monitoring method and daytime ABPM Secondary: sensitivity and specificity of each diagnostic method compared with daytime ABPM; adherence to and acceptability of each diagnostic method; BP reduction and hypertension diagnosis at 6 months; patient-reported quality of life related to physical health, anxiety, and lifestyle changes (physical activity and intake of fruits, vegetables, and salt) at 6 months |
| Timeframe | 3-week follow-up for primary outcome |
This randomized controlled trial compared the diagnostic performance, adherence, and acceptability of three monitoring methods to diagnose hypertension in patients with elevated BP.
Researchers used electronic health records (EHRs) to identify patients with elevated BP at their last clinic visit. Researchers then screened patients for elevated BP, and if elevated, randomly assigned patients to one of three BP monitoring methods:
- Clinic. Patients returned to the clinic once and a nurse or medical assistant checked their BP.
- Home. Patients checked their BP at home twice in the morning and twice in the evening for five days.
- Kiosk. Patients checked their BP at a clinic or pharmacy kiosk three times, waiting at least one minute between readings, each day for three days.
After three weeks, patients wore an ambulatory BP monitor for one day, which monitored their BP every 30 minutes during the daytime and every 60 minutes at night.
The study included 510 patients receiving care at one of 12 primary care centers from a healthcare organization in Washington State. Among patients, 80% were White, 7% were African American, 13% were another race, and 4% were Hispanic. The average age was 59, 52% were male, and average systolic BP was 150 mmHg at baseline.
Patients completed surveys at baseline, before and after ABPM, and again six months later.
Patients, providers, and other experts in BP measurement informed the study design and protocols.
Results
Compared with ABPM, patients’ mean systolic and diastolic BP
- Were lower with the clinic method (p<0.001)
- Did not differ significantly with the home method
- Were higher with the kiosk method (p<0.001)
The home and kiosk methods performed better than the clinic method, which missed hypertension more than half of the time. Diagnostic performance for each method was
- Clinic: 31.1% sensitivity; 79.5% specificity
- Home: 82.2% sensitivity; 53.3% specificity
- Kiosk: 96% sensitivity; 28.2% specificity
Compared with the clinic and home methods, patients using the kiosk method had lower adherence (87% clinic, 91% home, 68% kiosk; p=0.001). Patients found the home method more acceptable than clinic or kiosk methods (p<0.001).
After six months, across the three methods, patients had lower BP, but did not differ significantly in BP, physical health, or lifestyle changes.
Among participants who met criteria for hypertension based on ABPM, only 40% had a diagnosis of hypertension recorded in their EHR after six months.
Limitations
The study took place in one healthcare organization, and most patients were White. Results may differ in other organizations or for people from other backgrounds.
Conclusions and Relevance
In this study, monitoring BP at home had better diagnostic performance, adherence, and acceptability than at the clinic or kiosk. Most people with high blood pressure on ABPM did not receive a hypertension diagnosis.
Future Research Needs
Future research could test strategies for increasing home BP testing to diagnose hypertension.
Final Research Report
View this project's final research report
Journal Citations
Article Highlight: Proper diagnosis of hypertension can save a patient’s life. But blood pressure varies a lot over the day and one or two measurements in a clinic may not reflect a person’s average blood pressure. The BP-CHECK Study found that blood pressure measurements routinely taken at home are more likely to provide the basis for accurate diagnoses of hypertension than those taken in a clinic setting. The results were recently published in the Journal of General Internal Medicine. The study also found that blood pressure readings taken at home were consistent with the gold standard test for making a new diagnosis of high blood pressure. Blood pressure readings in clinics and kiosks resulted in a higher likelihood of missed diagnosis and overdiagnosis.
Results of This Project
Related Journal Citations
Peer-Review Summary
Peer review of PCORI-funded research helps make sure the report presents complete, balanced, and useful information about the research. It also assesses how the project addressed PCORI’s Methodology Standards. During peer review, experts read a draft report of the research and provide comments about the report. These experts may include a scientist focused on the research topic, a specialist in research methods, a patient or caregiver, and a healthcare professional. These reviewers cannot have conflicts of interest with the study.
The peer reviewers point out where the draft report may need revision. For example, they may suggest ways to improve descriptions of the conduct of the study or to clarify the connection between results and conclusions. Sometimes, awardees revise their draft reports twice or more to address all of the reviewers’ comments.
Peer reviewers commented and the researchers made changes or provided responses. Those comments and responses included the following:
- The reviewers asked the researchers to discuss further their observations regarding misclassification of hypertension in doctors’ offices and in pharmacy kiosks measuring blood pressure. The researchers explained that misclassification occurred differently in the two settings: at clinic sites, there was more underdiagnosis of hypertension, or false negatives, whereas at pharmacy kiosk sites, there was more overdiagnosis, or false positives. The researchers added discussion of false positive and false negative rates to the report’s abstract but noted that because these rates may be influenced by the prevalence of hypertension, they retained their reporting of sensitivity and specificity results as well.
- The reviewers asked how incomplete data, such as failure to complete the required number of measures, would affect the ability to make a correct hypertension diagnosis. The researchers interpreted this question as a concern regarding their use of a per-protocol analysis rather than an intent-to-treat analysis as originally planned. The researchers reanalyzed their data using an intent-to-treat model and conducted sensitivity analysis to test whether the missing data had an impact on study results. They found that missing data or incomplete measures had little impact on the results or on provider decision making.
- The reviewers challenged the researchers’ concerns about blood pressure measurements in pharmacy kiosks. The study found that blood pressure measures systematically ran high at these locations, but the reviewers conjectured that this was a positive aspect of these kiosks because the higher numbers would prompt the patient to start a conversation with their pharmacist or contact their doctor. The researchers acknowledged that this was true but noted that anxiety about consistently higher numbers might lead to overuse of medical appointments. The researchers also noted that in qualitative interviews, patients stated that they did not trust blood pressure readings from the kiosks and were significantly less likely to complete diagnostic testing if they received a high reading in this setting.
Conflict of Interest Disclosures
Project Information
Key Dates
Study Registration Information
^The original organization for the project was Group Health Cooperative.