Background

Hypertension is a common, long-term health condition that leads to increased cardiovascular morbidity and mortality, as well as increased consumption of health care resources. Effective treatments for hypertension are available; however, long-term adherence to medication and lifestyle modification remains a challenge. Self-measured blood pressure monitoring (SMBP) has been suggested as one method that may improve adherence to blood pressure (BP) treatment and consequently improve outcomes. SMBP refers to the regular self-measurement of a patient's BP at home or otherwise outside the office or clinic, as a supplement or alternative to those obtained in a health care setting. While patient self-participation in chronic disease management appears a promising means of improving adherence, the sustainability and clinical impact of this strategy, as well as its impact on health care utilization, remain uncertain.

The current Future Research Needs (FRN) project was launched upon the completion of an Agency for Healthcare Research and Quality (AHRQ) Comparative Effectiveness Review (CER) on SMBP, and builds on the evidence gaps identified in that review. The SMBP CER reviewed pertinent publications through July 2011 and identified 47 comparative studies of at least 8 weeks duration, and one observational study. For the comparison of SMBP alone versus usual care, the strength of evidence was moderate, supporting a lower BP with SMBP (SBP/DBP [systolic BP/diastolic BP] −3.1 / −2.0 mmHg at 6 months). For SMBP plus additional support versus usual care, the strength of evidence was high, supporting a lower BP with SMBP use (SBP/DBP −3.4 to −8.9 / −1.9 to −4.4 mmHg) at up to 12 months. For SMBP plus additional support versus SMBP alone or with less intense additional support, the strength of evidence was low, failing to support a difference in BP. For all comparisons, evidence for clinical outcomes was insufficient; for all other non-BP outcomes (surrogate and intermediate outcomes, and health care encounters) strength of evidence was low, failing to support a difference. No trials compared different SMBP devices or provided evidence on the relationship between BP control and clinical or surrogate outcomes. There was insufficient evidence concerning predictors of SMBP adherence. No studies in children were identified for the review.

The evidence gaps identified in the SMBP CER are summarized in Table A, organized and labeled by Key Question and PICOD (Population, Intervention, Comparator, Outcome, study Design) category. These gaps limited the conclusions that could be drawn in the original CER, and thus became the initial list of priority topics for the present FRN project. Figure A depicts the analytic framework used to guide the Key Questions for the CER of SMBP, with the addition of annotations indicating evidence gaps. Although the evidence gap in children was noted, it was determined that the current project proceed with a focus on adults only, as refinement of the future research agenda in children would require a specially composed stakeholder group.

Table A

Identified evidence gaps organized by relevant Key Question and PICOD element.

Figure A

Analytic framework for SMBP with evidence gaps. Abbreviations: AE=adverse events; BP=blood pressure; CVD=cardiovascular disease; KQ=Key Question; LVH=left ventricular hypertrophy; LVM=left ventricular mass; LVMI=left ventricular mass index; SMBP=self-measured (more...)

Methods

Results

Based on the SMBP CER and our discussion with stakeholders, 16 future research needs topics were nominated. The topics chosen as the highest priority future research needs are listed in Table B.

Table B

The top five priority future research needs as indicated by participating stakeholders.

The first four topics pertain to interrelated evidence gaps such as the lack of longer term studies which show persistence of BP control or clinical benefit from SMBP, uncertainty regarding who is likely to benefit from SMBP, lack of standardization in prescription of SMBP, and uncertainty regarding the most effective additional support. The fifth topic relates to the inability to assess cost-effectiveness of SMBP, due to the deficiencies in evidence identified in the first four gaps.

Hypertension is a long-term condition and BP changes with age, acute illness, and comorbidities achieving optimal control requires long-term monitoring. The benefits of long-term BP control are presumed to include a reduction in clinical cardiovascular outcomes; therefore, the need to demonstrate that SMBP has long-term benefit is paramount to establishing a justification for SMBP. This is particularly pertinent, since SMBP requires long-term patient participation. Thus, the first topic (Topic 1) is focused on the need for longer term studies and plays a central role also for the remaining topics. At the same time, since long-term effects of SMBP may be modulated by patient and disease factors, SMBP prescription, and types of additional support, considerations for Topics 2, 3, and 4 affect research design deliberations for Topic 1.

Longer term trials are necessary in order to address FRN Topic 1. Clinical outcome trials, while providing the most rigorous information on comparative effectiveness, do not appear feasible given the large sample sizes necessary. Embedding the study of SMBP in another large trial of a CVD (cardiovascular disease) risk reduction strategy, however, might be a viable alternative. Also, it may be possible to extrapolate from a large body of experimental evidence that links BP reduction with improved clinical outcomes to SMBP. However, longer term clinical trials of SMBP that assess adherence with SMBP, adherence with prescribed medications, BP control, and patient satisfaction are feasible and necessary to address the question of whether the SMBP effect is durable. Observational studies comparing outcomes in SMBP users versus nonusers are confounded, and this bias cannot be satisfactorily overcome.

For FRN Topic 2, modeling can be used to explore the heterogeneity of treatment effects, using individual patient data from trials or observational studies to develop and validate predictive instruments for SMBP adherence or BP control. Candidate predictor variables include sex, age, race/ethnicity, socioeconomic status, disease characteristics, and cardiovascular disease risk factors, as well as attitudes regarding participation in disease management. Using these instruments prospectively may circumvent the problem of multiple subgroup comparisons in future trials.

With regards to FRN Topic 3, SMBP prescriptions ought to be standardized based on randomized controlled trials comparing different prescriptions and their effect on adherence to SMBP, adherence to BP medication and BP control.

For FRN Topic 4, an expert panel should be employed to prioritize what elements of additional support should be chosen for future comparative studies of SMBP. The panel should include pharmacists, experts in telemedicine and bioinformatics, and authorities in adherence and chronic disease management.

To address FRN Topic 5, which was outside the scope of the SMBP CER, a systematic review of the existing cost-effectiveness analyses would be the first step. Longer term SMBP studies of BP outcomes and resource use (and possibly clinical outcomes and subgroup effects) are needed to assess the overall balance of costs and benefits of SMBP.

Discussion

The prioritization of topics for future research was generated based on a stakeholder-driven nomination and prioritization process. Our stakeholder panel represented a broad range of perspectives, across major stakeholder categories identified in this taxonomy. We were able to obtain input from all panel members, and the final ranking showed a clear separation of the top priorities.

Nevertheless, the process was not without limitations. The total number of stakeholders recruited was restricted, thus limiting representation. Also, despite formal planning, the selection of stakeholders, solicitation of contributions, facilitation of discussion, and synthesis of suggestions remain, to some degree, idiosyncratic.

One additional crosscutting methodological issue outside of the scope of the SMBP CER relates to the challenge of translating BP readings obtained at home, in the clinic, or by ambulatory BP monitoring. Once it is possible to convert between home BP, clinic BP, and ambulatory BP readings, BP can be assessed comprehensively across different settings, and consistent targets can be set.

Conclusions

This report identifies five high-priority future research needs with regards to SMBP, as determined by a stakeholder panel. They are:

1. What are the effects of SMBP on BP, medication adherence rates, satisfaction, and clinical event outcomes, after longer followup periods of 2 to 5 years or longer?
2. Which patients may be more likely to benefit from using SMBP?
3. What is the best prescription or protocol for SMBP (when, how often, and how frequently)? How do different prescriptions for SMBP compare regarding acceptance by patients, adherence with SMBP, and effect on BP control?
4. What is the role of additional support? What particular components of additional support should be further evaluated?
5. What is the effect of SMBP on resource utilization? What is the cost-effectiveness of SMBP?

In summary, to address these gaps: longer term randomized controlled trials that examine SMBP's effects on BP control and resource utilization are needed; the impact of SMBP on CVD outcomes may be gleaned from embedding SMBP in other CVD outcome trials; the exploration of treatment heterogeneity may identify those groups more likely to benefit from SMPB. When, how often, and how frequently to use SMBP, and what additional support to employ, should be further refined. Finally, filling these evidence gaps will inform future modeling of cost-effectiveness.