Twenty-four-hour ambulatory blood pressure monitoring in hypertension: an evidence-based analysis.

Objective: The objective of this health technology assessment was to determine the clinical effectiveness and cost-effectiveness of 24-hour ambulatory blood pressure monitoring (ABPM) for hypertension.

Clinical Need: Condition And Target Population: Hypertension occurs when either systolic blood pressure, the pressure in the artery when the heart contracts, or diastolic blood pressure, the pressure in the artery when the heart relaxes between beats, are consistently high. Blood pressure (BP) that is consistently more than 140/90 mmHg (systolic/diastolic) is considered high. A lower threshold, greater than 130/80 mmHg (systolic/diastolic), is set for individuals with diabetes or chronic kidney disease. In 2006 and 2007, the age-standardized incidence rate of diagnosed hypertension in Canada was 25.8 per 1,000 (450,000 individuals were newly diagnosed). During the same time period, 22.7% of adult Canadians were living with diagnosed hypertension. A smaller proportion of Canadians are unaware they have hypertension; therefore, the estimated number of Canadians affected by this disease may be higher. Diagnosis and management of hypertension are important, since elevated BP levels are related to the risk of cardiovascular disease, including stroke. In Canada in 2003, the costs to the health care system related to the diagnosis, treatment, and management of hypertension were over $2.3 billion (Cdn).

Technology: The 24-hour ABPM device consists of a standard inflatable cuff attached to a small computer weighing about 500 grams, which is worn over the shoulder or on a belt. The technology is noninvasive and fully automated. The device takes BP measurements every 15 to 30 minutes over a 24-to 28-hour time period, thus providing extended, continuous BP recordings even during a patient’s normal daily activities. Information on the multiple BP measurements can be downloaded to a computer. The main detection methods used by the device are auscultation and oscillometry. The device avoids some of the pitfalls of conventional office or clinic blood pressure monitoring (CBPM) using a cuff and mercury sphygmomanometer such as observer bias (the phenomenon of measurement error when the observer overemphasizes expected results) and white coat hypertension (the phenomenon of elevated BP when measured in the office or clinic but normal BP when measured outside of the medical setting).

Research Questions: 1. Is there a difference in patient outcome and treatment protocol using 24-hour ABPM versus CBPM for uncomplicated hypertension? 2. Is there a difference between the 2 technologies when white coat hypertension is taken into account? 3. What is the cost-effectiveness and budget impact of 24-hour ABPM versus CBPM for uncomplicated hypertension?

Research Methods: LITERATURE SEARCH: SEARCH STRATEGY: A literature search was performed on August 4, 2011 using OVID MEDLINE, MEDLINE In-Process and Other Non-Indexed Citations, EMBASE, the Cumulative Index to Nursing and Allied Health Literature (CINAHL), the Cochrane Library, and the International Agency for Health Technology Assessment (INAHTA) for studies published from January 1, 1997 to August 4, 2011. Abstracts were reviewed by a single reviewer. For those studies meeting the eligibility criteria, full-text articles were obtained. Reference lists were also examined for any additional relevant studies not identified through the search. Articles with unknown eligibility were reviewed with a second clinical epidemiologist and then a group of epidemiologists until consensus was established. The quality of evidence was assessed as high, moderate, low, or very low according to GRADE methodology. INCLUSION CRITERIA: English language articles; published between January 1, 1997 and August 4, 2011; adults aged 18 years of age or older; journal articles reporting on the effectiveness, cost-effectiveness, or safety for the comparison of interest; clearly described study design and methods; health technology assessments, systematic reviews, meta-analyses, or randomized controlled trials. EXCLUSION CRITERIA: non-English papers; animal or in vitro studies; case reports, case series, or case-case studies; studies comparing different antihypertensive therapies and evaluating their antihypertensive effects using 24-hour ABPM; studies on home or self-monitoring of BP, and studies on automated office BP measurement; studies in high-risk subgroups (e.g. diabetes, pregnancy, kidney disease). OUTCOMES OF INTEREST: PATIENT OUTCOMES: mortality: all cardiovascular events (e.g., myocardial infarction [MI], stroke); non-fatal: all cardiovascular events (e.g., MI, stroke); combined fatal and non-fatal: all cardiovascular events (e.g., MI, stroke); all non-cardiovascular events; control of BP (e.g. systolic and/or diastolic target level). DRUG-RELATED OUTCOMES: percentage of patients who show a reduction in, or stop, drug treatment; percentage of patients who begin multi-drug treatment; drug therapy use (e.g. number, intensity of drug use); drug-related adverse events.

Quality Of Evidence: The quality of the body of evidence was assessed as high, moderate, low, or very low according to the GRADE Working Group criteria. As stated by the GRADE Working Group, the following definitions of quality were used in grading the quality of the evidence: [Table: see text]

Summary Of Findings: SHORT-TERM FOLLOW-UP STUDIES (LENGTH OF FOLLOW-UP OF ≤ 1 YEAR): Based on very low quality of evidence, there is no difference between technologies for non-fatal cardiovascular events. Based on moderate quality of evidence, ABPM resulted in improved BP control among patients with sustained hypertension compared to CBPM. Based on low quality of evidence, ABPM resulted in hypertensive patients being more likely to stop antihypertensive therapy and less likely to proceed to multi-drug therapy compared to CBPM. Based on low quality of evidence, there is a beneficial effect of ABPM on the intensity of antihypertensive drug use compared to CBPM. Based on moderate quality of evidence, there is no difference between technologies in the number of antihypertensive drugs used. Based on low to very low quality of evidence, there is no difference between technologies in the risk for a drug-related adverse event or noncardiovascular event. LONG-TERM FOLLOW-UP STUDY (MEAN LENGTH OF FOLLOW-UP OF 5 YEARS): Based on moderate quality of evidence, there is a beneficial effect of ABPM on total combined cardiovascular events compared to CBPM. Based on low quality of evidence, there is a lack of a beneficial effect of ABPM on nonfatal cardiovascular events compared to CBPM; however, the lack of a beneficial effect is based on a borderline result. Based on low quality of evidence, there is no beneficial effect of ABPM on fatal cardiovascular events compared to CBPM. Based on low quality of evidence, there is no difference between technologies for the number of patients who began multi-drug therapy. Based on low quality of evidence, there is a beneficial effect of CBPM on control of BP compared to ABPM. This result is in the opposite direction than expected. Based on moderate quality of evidence, there is no difference between technologies in the risk for a drug-related adverse event.