Introduction

Arterial hypertension is the most important risk factor affecting cardiovascular, cerebrovascular, and renal disease-related morbidity and mortality.^1,2 The prevalence of hypertension was estimated to be 1.13 billion in 2015, and the number of patients is expected to increase by 15-20% to approach 1.5 billion by 2025. The overall prevalence of hypertension in adults is around 30-45%.^3-5

Hypertension is mostly asymptomatic, and BP measurement scans show that more than half of the patients are unaware of their high BP.⁴ The inadequacy of office blood pressure measurements (OBPMs) in diagnosing hypertension has increased the need for out-of-office blood pressure monitoring.¹ Such as home blood pressure monitoring (HBPM) and ambulatory blood pressure monitoring (ABPM), which are more closely associated with the risk of organ damage and cardiovascular events caused by hypertension than in-office measurements. It also has advantages such as detecting white coat and masked hypertension.^1,2,6

Home blood Pressure monitoring is much less expensive than ABPM and can demonstrate day-to-day BP variability, which has prognostic value because multiple measurements are taken over several days.⁷

Home BP measurements are required for the diagnosis of hypertension due to the limited availability of ABPM devices, high cost, patient density, and non-compliance with ABPM. It has been shown that HBPMs are often inaccurate and unreliable due to improper preparation, suboptimal environments, inappropriate devices, and insufficient patient information about the measurement techniques.⁸ Because the threshold for HT diagnosis is the same with HBPM and the daytime values of ABPM (135/85 mmHg), we hypothesize that training and adherence to the recommended home BPM method will reflect hypertensive patients more accurately when daytime ABPM results are taken as reference.

This study was designed to evaluate the effect of training on and adherence to the recommended methods of HBPM and to compare the results with and without structured training.

Methods

This study was conducted in the Cardiology Outpatient Clinics of Gülhane Training and Research Hospital between January 1, 2021, and June 30, 2021.

Patients admitted to the outpatient clinic who were older than 18 years of age had no previous diagnosis of hypertension, had an OBPM between systolic 140 and 180 mm Hg and/or diastolic 90 and 110 mm Hg, and were recommended HBPM by a physician were included in the study. Patients with a previous diagnosis of hypertension, who had been started on antihypertensive treatment in the past and had systolic blood pressure (SBP) >180 mm Hg and diastolic blood pressure (DBP) >110 mm Hg were excluded.

Calibrated Omron M7 Intelligent BP monitors were used for office and home measurements, and Mobil-O-Graph brand ambulatory BP monitors were used for ambulatory measurements. OBPM, HBPM, and ABPM measurements of the patients were performed with the same devices when the measurements were repeated.

After enrollment in the first visit, the patients were given a brochure on lifestyle changes prepared according to World Health Organization “Healthy living” recommendations and 2 weeks to implement these recommendations without measuring their BP unless needed. We prepared an educational brochure entitled “How to measure blood pressure at home?” and a questionnaire entitled “Test for Accurate Blood Pressure Measurement at Home” according to the guidelines.^1,2,9 The questionnaire consisted of 26 yes/no questions to understand how the patient measured BP correctly in accordance with the recommendations. One point for correct answers and zero points for false answers were given. The patients took the test twice, once after they measured their BP at home before training (pre-test) and once after training (post-test).

Training on accurate BP measurement at home was explained to the patients one by one in detail. It was recommended to measure BP in the morning after waking up and in the evening before going to bed. We explained the measurement style in 3 stages as follows: preparation, position, and measurement.

Preparation

Position

Measure

The actions in each step according to the study protocol were as follows (Figure 1):

The present study was approved by the Local Ethics Committee (Approval number: 2020/521). Informed consent was submitted by all subjects when they enrolled.

Statistical Analysis

Sample size: Assuming a standard deviation of 10 mmHg, it was calculated that to find a 6 mm Hg difference in DBP “significant” by the home measurement method with an alpha of 5% (two-way) and a power of 90%, at least 60 individuals in each group (total sample size of 120 patients) were required.¹¹

The suitability of the variables for normal distribution was determined by Shapiro-Wilk and Kolmogorov-Smirnov tests, skewness and kurtosis values, histogram graphs, mean ± SD, and median values. Numeric data that fit the normal distribution are expressed as arithmetic mean ± SD, and data not normally distributed are expressed as median with data range (minimum-maximum). Categorical data are expressed as counts and percentages. Paired-Samples t-test was used for comparisons between dependent groups of continuous numerical data that fit the normal distribution, and Wilcoxon Signed Ranks test was used for non-parametric data that did not fit the normal distribution. McNemar Chi-square test was used for comparisons of categorical data between dependent groups (repeated measurements). A value of P < 0.05 was considered to be statistically significant. Analyses were performed using SPSS 25.0 program.

Results

The study included 129 patients [59 (45.7%) female and 70 (54.3%) male]. The mean age of the patients was 45.10 ± 10.91 years. Baseline characteristics of the patients included in the study are presented in Table 1.

Post-test scores increased after training (from 19 (14-26) pre-training to 26 (23-29) post-training (median (min-max); P < .001), showing that adherence to the guideline recommendations on HBPM with training increased significantly.

Systolic and diastolic BP as well as heart rate measured with the HBPM device were decreased after training compared to the pre-training course (Table 2). However, none of these values measured with ABPM (including daytime, nighttime, and 24 hours) were different between pre- and post-training measurements (Table 3).

When HBPM and ABPM measurements before and after the training were compared, ABPM values were higher than those of HBPM both before and after training. However, the difference increased after training, mainly due to the decreased values of HBPM after training (Table 4). Consistent with these findings, the number of patients meeting the hypertension criteria with HBPM decreased from 71 (55%) to 54 (41.9%) after training (P = .006), whereas the number of patients diagnosed as hypertensive did not change with daytime ABPM (82 (64.3%) before vs. 84 (65.1%) after training; P = 1.000) (Table 5).

Before and after the training, the diagnosis of HT by HBPM and ABPM was compared. Before the training, 76.7% of the patients were diagnosed with HT with 24-hour ABPM and 64.3% with daytime ABPM, while 55.0% of the patients were diagnosed with HT with HBPM (P < .001, P = .043, respectively). After the training, the percentage of HT diagnosis with 24-hour ABPM and with daytime ABPM was 75.2% and 41.9%, respectively (P < .001). This difference still remained statistically significant after only the daytime values of ABPM were taken for HT diagnosis (65.1% for ABPM vs. 41.9%; P < .001) (Table 6).

The number of patients diagnosed with hypertension according to different measurement methods at HBPM and ABPM Day is shown in Figure 2.

Discussion

The results of this study show that training on and good adherence to HBPM instructions caused lower BP values to be obtained and a smaller number of patients to receive a diagnosis of hypertension compared to those before structured training. Contrary to our hypothesis, with training and adherence to the instructions, the gap between HBPM and daytime ABPM widened in terms of BP values, and the number of patients diagnosed with hypertension decreased when daytime ABPM is taken as a standard.

It has been shown that both OBPM and out-of-office BP elevation are associated with cardiovascular, cerebrovascular, and renal disease.^12-14 Standard OBPM is the best-studied method for diagnosing hypertension, assessing the protective effect of antihypertensive treatment, and monitoring BP goals with therapeutic interventions. Although inaccurate results are encountered due to inadequate standardization and improper measurements, OBPM is still a frequently used BP measurement method.^2,15 In clinical studies, when OBPM and ABPM are compared, there are opinions that office measurements are inadequate in predicting cardiovascular outcomes and do not have sufficient reliability.^16-19

There are suggestions that ambulatory monitoring may lead to more appropriate treatment targeting, rather than initiating antihypertensive treatment based solely on office measurements.²⁰

Of the 129 patients included in our study who were considered hypertensive according to office BP, 99 patients (76.7%) met the hypertension criteria according to their ABPM (24 hours) (Table 5). As supported by a substantial number of studies, relying solely on single office measurements would overestimate the number of hypertensive patients.

On the other hand, HBPM is an alternative out-of-office BP monitoring method that is widely used in clinical practice and advised by the guidelines to be used for this purpose.²¹ The diagnostic performance of HBPM has been shown to be slightly higher than OBPM, and both methods have similar prognostic value.¹⁹

Home blood pressure monitoring and ABPM provide multiple measurements taken outside the office in the individual’s usual environment. There are methodological differences between HBPM and ABPM. Although HBP is measured only at home in a standardized sitting situation throughout the day, ABPM is measured in different situations such as lying, sitting, and standing, and during daytime activities and night sleep in different environments such as work and home. Despite this difference, the criteria for HT diagnosis with HBPM and daytime values of ABPM are the same (≥135/85 mm Hg). In our study, even if only the daytime values of ABPM were used, the frequency of HT diagnosis was still higher with ABPM compared to HBPM (64.3% for ABPM vs. 55.0%; P = .043) (Table 6).

Home blood pressure monitoring has important limitations such as the necessity of patient education, measurement with unstandardized devices, and anxiety during measurement.²¹

It has been shown that accurate reporting of measurements should be ensured in HBPM, and that measurements reported by patients differ from frequently measured values. In surveys of primary care physicians conducted in different countries, it has been reported that the reliability of patients’ home BP readings is questionable and that their clinical use is unreliable.^22-24

It is conceivable that standardizing the measurement method, appropriate measurement conditions, and patient education may increase the reliability of HBP measurements. In our study, appropriately calibrated devices that store records were used.

After training, the measurements were extremely standardized and made in resting and proper sitting conditions, in isolated environments, at least twice and after emptying the bladder, as stated in the guidelines. As a result, the frequency of HT diagnosis according to home measurements decreased from 55.0% to 41.9% after the training (P = .006) (Table 5). As expected, 24-hour ABPM and HT diagnosis status did not change between the 2 measurements as training did not change the ABPM style. We hypothesized that training would decrease the difference in HT diagnosis between the ABPM and HBPM systems as supposed to be, but unexpectedly, this difference increased, raising the question of which method is the best for out-of-office measurement and has the best prognostic value.

Our study showed that “dedicated” training increased patient compliance and worked well regarding standardization, as the “correct blood pressure measurement score” increased significantly. In a study examining how closely patients attending a hypertension clinic complied with recommendations for appropriate home BP measurement, it was concluded that patients tend to show their compliance in measuring better than they actually do.²⁵ It has been shown that more than half of the patients record their home BP readings when symptoms occur rather than at the recommended times.⁸ In our study the measurements were independent of the symptoms and were made according to the guidelines. Another point is that it has been noted that patients may tend to make their home readings look better than they really are, and devices with memory should therefore be used.²⁵ Therefore, we verified the patient recordings with the device memory, which showed excellent patient self-recordings.

The reason why the post-training BP values were lower may be that the measurements were made in an extremely isolated and “sterile” environment, as guidelines stated. But it is an important concern how much the BP values obtained with this strategy reflect daily life and predict the prognosis. It is known that OBPM, HBPM, and ABPM measurements each provide different and complementary information about the clinical situation. There is no clear information on which patients and when ABPM or HBPM should be used. The decision to use ABPM or HBPM may be the patient’s preference and is also related to the availability and reimbursement policy of health care systems. It is often not possible to use these methods, particularly ABPM, in daily practice, which may make HBPM the preferred out-of-office BPM method. Training of patients who are being evaluated with HBPM is an essential step for standardization, as verified in our study. This study also showed that standardization in HBPM, as recommended in guidelines, decreased the mean BP values as well as the number of HT diagnoses in comparison to daytime ABPM. But the difference in HT diagnosis between the ABPM and HBPM increased. Considering the high prevalence of HT in the population, this difference may have a major impact not only on an individual level but also on the population level and in the determination of health care policies.

Study Limitations

There are several limitations in this study.

First, this study is not designed to provide prognostic data on which method is the best in terms of non-clinical (proteinuria, left ventricular hypertrophy, etc.) or clinical (stroke, myocardial infarction, etc.) endpoints. Obviously, the best method of out-of-office measurements and new thresholds could be defined with such studies.

Second, no verification could be made regarding how well the patients complied with the training provided. However, post-test scores increased according to self-reported questionnaires.

Third, a substantial number of patients did not have hypertension with both modalities. Because the main purpose of out-of-office BP measurement methods is to eliminate white coat hypertension, this result was consistent with real life.

We believe that the design of the study and the careful application of the study protocol are the major strengths of the current study. Before evaluation with out-of-office methods, we gave time for the implementation of lifestyle changes. In addition, we used exactly the same automated HBP and ABP devices for the particular patient before and after training. Also, there was no loss to follow up.

Conclusion

The training of patients to standardize HBPM has an important effect on the diagnosis of HT, with lower BP values and fewer patients diagnosed with HT in a group of patients with office BP between 140-180/90-110 mm Hg and without a previous hypertension diagnosis. Compared with ABPM, the number of HT diagnoses was less with HBPM and decreased after training to standardize the HBPM method. It can be speculated that current recommendations on HBPM may not reflect BP in daily life and underestimate the number of hypertensive patients. Rather than measurement at predefined times, multiple random measurements might be preferred. In order to test this hypothesis, prospective studies with clinical or non-clinical endpoints are needed.

Footnotes

Ethics Committee Approval: The present study was approved by the University of Health Sciences Gülhane Scientific Research Ethics Committee (Approval date: 29.11.2020, Approval number: 2020/521).

Informed Consent: Informed consent was submitted by all subjects when they enrolled.

Peer-review: Internally peer-reviewed.

Author Contributions: Concept – H.S., C.B., A.A.; Design – H.S., İ.S.G., G.K.; Supervision – H.S., C.B., A.Ç.Ş.; Resources – A.A., C.B., A.Ö., S.Y.; Data Collection and/or Processing – A.A., F.S.K., G.K.; Analysis and/or Interpretation – H.S., A.A., C.B., İ.S.G.; Literature Search – H.S., A.A., A.Ö., S.Y.; Writing – H.S., C.B., A.A., A.Ö.; Critical Review – H.S., C.B., A.Ö., A.Ç.Ş.

Declaration of Interests: The authors have no conflicts of interest to declare.

References

1. Whelton PK, Carey RM, Aronow WS. 2017 ACC/AHA/AAPA/ABC/ACPM/AGS/APhA/ASH/ASPC/NMA/PCNA guideline for the prevention, detection, evaluation, and management of high blood pressure in adults: executive summary: a report of the American College of Cardiology/American Heart Association Task Force on Clinical Practice guidelines. Hypertension. 2018;71(6):1269-1324. https://doi.org/10.1161/HYP.0000000000000066
2. Williams B, Mancia G, Spiering W. Practice Guidelines for the management of arterial hypertension of the European Society of Cardiology and the European Society of Hypertension. J Hypertens. 2018;36(12):2284-2309. https://doi.org/10.1097/HJH.0000000000001961
3. Zhou B, Bentham J, Di Cesare M. Worldwide trends in blood pressure from 1975 to 2015: a pooled analysis of 1479 population-based measurement studies with 19·1 million participants. Lancet. 2017;389(10064):37-55. https://doi.org/10.1016/S0140-6736(16)31919-5
4. Chow CK, Teo KK, Rangarajan S. Prevalence, awareness, treatment, and control of hypertension in rural and urban communities in high-, middle-, and low-income countries. JAMA. 2013;310(9):959-968. https://doi.org/10.1001/jama.2013.184182
5. Kearney PM, Whelton M, Reynolds K, Muntner P, Whelton PK, He J. Global burden of hypertension: analysis of worldwide data. Lancet. 2005;365(9455):217-223. https://doi.org/10.1016/S0140-6736(05)17741-1
6. Unger T, Borghi C, Charchar F. 2020 International Society of Hypertension Global Hypertension Practice Guidelines. Hypertension. 2020;75(6):1334-1357. https://doi.org/10.1161/HYPERTENSIONAHA.120.15026
7. Kikuya M, Ohkubo T, Metoki H. Day-by-day variability of blood pressure and heart rate at home as a novel predictor of prognosis: the Ohasama study. Hypertension. 2008;52(6):1045-1050. https://doi.org/10.1161/HYPERTENSIONAHA.107.104620
8. Milot JP, Birnbaum L, Larochelle P. Unreliability of home blood pressure measurement and the effect of a patient-oriented intervention. Can J Cardiol. 2015;31(5):658-663. https://doi.org/10.1016/j.cjca.2015.03.006
9. AHA-AMA SMBP. Infographic – Target:BP. . ;():-. https://targetbp.org/tools_downloads/how-to-accurately-measure-blood-pressure-2/
10. . Healthy living tips for those with chronic diseases. . ;():-. https://hsgm.saglik.gov.tr/depo/birimler/kronik-hastaliklar-ve-yasli-sagligi-db/Dokumanlar/Afisler/Kronik_Hastal_Olan_Bireyler_i_in_Sa_l_kl_Ya_am_nerileri.pdf
11. Niiranen TJ, Mäki J, Puukka P, Karanko H, Jula AM. Office, home, and ambulatory blood pressures as predictors of cardiovascular risk. Hypertension. 2014;64(2):281-286. https://doi.org/10.1161/HYPERTENSIONAHA.114.03292
12. Visseren FLJ, Mach F, Smulders YM. 2021 ESC Guidelines on cardiovascular disease prevention in clinical practice. Eur Heart J. 2021;42(34):3227-3337. https://doi.org/10.1093/eurheartj/ehab484
13. . Guideline for the pharmacological treatment of hypertension in adults. . ;():-. https://www.who.int/publications/i/item/9789240033986
14. Lewington S, Clarke R, Qizilbash N, Peto R, Collins R. Age-specific relevance of usual blood pressure to vascular mortality: a meta-analysis of individual data for one million adults in 61 prospective studies. Lancet. 2002;360(9349):1903-1913. https://doi.org/10.1016/S0140-6736(02)11911-8
15. Stergiou GS, Palatini P, Parati G. 2021 European Society of Hypertension practice guidelines for office and out-of-office blood pressure measurement. J Hypertens. 2021;39(7):1293-1302. https://doi.org/10.1097/HJH.0000000000002843
16. Ohkubo T, Hozawa A, Nagai K. Prediction of stroke by ambulatory blood pressure monitoring versus screening blood pressure measurements in a general population: the Ohasama study. J Hypertens. 2000;18(7):847-854. https://doi.org/10.1097/00004872-200018070-00005
17. Verdecchia P. Prognostic value of ambulatory blood pressure: current evidence and clinical implications. Hypertension. 2000;35(3):844-851. https://doi.org/10.1161/01.HYP.35.3.844
18. Whitworth JA. 2003 World Health Organization (WHO)/International Society of Hypertension (ISH) statement on management of hypertension. J Hypertens. 2003;21(11):1983-1992. https://doi.org/10.1097/00004872-200311000-00002
19. Hodgkinson J, Mant J, Martin U. Relative effectiveness of clinic and home blood pressure monitoring compared with ambulatory blood pressure monitoring in diagnosis of hypertension: systematic review. BMJ. 2011;342():d3621-. https://doi.org/10.1136/bmj.d3621
20. McCormack T, Krause T, O’Flynn N. Management of hypertension in adults in primary care: NICE guideline. Br J Gen Pract. 2012;62(596):163-164. https://doi.org/10.3399/bjgp12X630232
21. Parati G, Stergiou GS, Bilo G. Home blood pressure monitoring: methodology, clinical relevance and practical application: a 2021 position paper by the Working Group on Blood Pressure Monitoring and cardiovascular variability of the European Society of Hypertension. J Hypertens. 2021;39(9):1742-1767. https://doi.org/10.1097/HJH.0000000000002922
22. Tsakiri C, Stergiou GS, Boivin JM. Implementation of home blood pressure monitoring in clinical practice. Clin Exp Hypertens. 2013;35(7):558-562. https://doi.org/10.3109/10641963.2013.764890
23. Logan AG, Dunai A, McIsaac WJ, Irvine MJ, Tisler A. Attitudes of primary care physicians and their patients about home blood pressure monitoring in Ontario. J Hypertens. 2008;26(3):446-452. https://doi.org/10.1097/HJH.0b013e3282f2fdd4
24. Boivin JM, Tsou-Gaillet TJ, Fay R, Dobre D, Rossignol P, Zannad F. Influence of the recommendations on the implementation of home blood pressure measurement by French general practitioners: a 2004-2009 longitudinal survey. J Hypertens. 2011;29(11):2105-2115. https://doi.org/10.1097/HJH.0b013e32834b7efb
25. Pickering TG, Miller NH, Ogedegbe G. Call to action on use and reimbursement for home blood pressure monitoring: executive summary: a joint scientific statement from the American Heart Association, American Society Of Hypertension, and Preventive Cardiovascular Nurses Association. Hypertension. 2008;52(1):1-9. https://doi.org/10.1161/HYPERTENSIONAHA.107.189011