Hypertension Journal

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Recommended Standards for assessing Blood Pressurein Human Research where Blood Pressure orHypertension is a Major Focus
Recommended Standards for assessing Blood Pressure
in Human Research where Blood Pressure or
Hypertension is a Major Focus
Norm RC Campbell
Department of Medicine, Community Health Sciences, Physiologyand Pharmacology, O'Brien Institute of Public Health and LibinCardiovascular Institute of Alberta, University of Calgary, CalgaryAlberta, Canada
Correspondence Author: Norm RC Campbell, ProfessorDepartment of Medicine, Community Health Sciences, Physiologyand Pharmacology, O'Brien Institute of Public Health and LibinCardiovascular Institute of Alberta, University of Calgary, CalgaryAlberta, Canada
Phone: +4032107961
e-mail: achob@bu.edu
National and international recommendations for assessingblood pressure advocate for specific training and accuracyassessment of observers, use of a standardized technicalprocedure, as well as use of accurate and appropriate equipment.However, these recommendations are often not adheredto even in research studies that relate directly to blood pressureor antihypertensive therapies. Inaccurate, nonreproducibleblood pressure values can result from nonstandardizedassessments, and impair the ability to define the populationbeing studied; fail to identify people who are susceptible tohypotensive adverse events; and reduce the ability to assessthe impact of interventions on blood pressure. A consortium ofnational and international health and scientific organizationsoversaw an expert review and consensus process to developminimum standards for assessing blood pressure in humanclinical and epidemiological research patients where (1) bloodpressure or hypertension is a major endpoint, or (2) blood pressureor hypertension is thought to be a major mediator of theresearch outcome (e.g., a study on an antihypertensive therapyor lifestyle change with a cardiovascular outcome). Minimumstandards are presented for training of observers, technicalaspects of assessing blood pressure, and equipment used,based on existing national and international recommendations.A limitation is that some existing recommendation processeswere not systematic or did not assess the strength of evidencesupporting specific recommendations. Funding agencies,journal editors, and reviewers should require adherence tothese minimum standards for all new research on the patientpopulations described above. Researchers should modifytheir study designs to meet the minimum standards. Readersneed to use caution in interpreting studies if the standardsare not met.
Keywords: Blood pressure, Blood pressure measurement,Epidemiology, Hypertension, Research, Research standards.
How to cite this article: Campbell NRC. RecommendedStandards for assessing Blood Pressure in Human Researchwhere Blood Pressure or Hypertension is a Major Focus.Hypertens J 2017;3(1):1-6.
Source of support: Funding was provided by the Heart andStroke Foundation (Canada), Canadian Institute for HealthResearch Chair in Hypertension Prevention and Control withkind support from the World Hypertension League.
Conflict of interest: Specific conflicts of interest for eachmember of the TRUE Consortium can be found in Appendix A.The findings and conclusions in this report are those of theauthors and do not necessarily represent the official positionof the Centers for Disease Control and Prevention.


Standardized and rigorous methods for blood pressuremeasurement are necessary to ensure the comparabilityand accuracy of blood pressure assessments forindividuals due to the effects of measurement error,diurnal variation, and short- and long-term variability.1-10 Many studies have demonstrated substantivechanges in blood pressure related to methodologicalissues when the blood pressure assessment did notsatisfy the established standards.6,8,11-13 It is thoughtthat a lack of rigor/standardization in assessing bloodpressure may reduce or mask the relationship betweenblood pressure, lifestyle changes, or antihypertensivemedications and adverse outcomes. For example, theINTERHEART study assessed blood pressure statussolely by asking participants if they had been diagnosedwith hypertension in many countries where awarenessof hypertension diagnosis was low.14 Not surprisingly,the INTERHEART study found hypertension to be thesixth leading risk for acute myocardial infarction, whilebased on numerous studies, there is a consensus thatincreased blood pressure is the leading risk for ischemicheart disease.15 The INTERHEART findings couldmislead policymakers that hypertension control is notas high a priority intervention as interventions on risksthat ranked higher. Further, observations of nonbloodpressure-lowering effects of antihypertensive drugs maybe attributed to inadequate assessment of blood pressureor inadequate assessment of blood pressure could limitthe ability to detect cardiac effects of noncardiovascular drugs or their interaction with other medications.16-18Nevertheless, many investigators historically have notpublished the training and accuracy testing of thoseassessing blood pressure, and have not indicated thetechnical and methodological aspects of assessing bloodpressure in clinical research studies where blood pressurewas a major focus.19

An inTernational consoRtium for qUality resEarch(TRUE) on dietary sodium/salt was formed to makerecommendations to improve the quality of researchon dietary salt. Lack of standardization and quality ofblood pressure measurement was viewed as a factor,creating controversy about the relationship of dietary saltto increased blood pressure and hypertension. Initiallyfocused on setting recommended standards for assessingblood pressure in human studies on dietary salt, themandate was expanded, recognizing low-quality bloodpressure assessment as a widespread issue with thepotential to adversely impact all human blood pressureresearch.

The recommendations below are intended to beapplied to human clinical and epidemiological researchwhere (1) blood pressure or hypertension is a major endpoint,or (2) blood pressure or hypertension is thoughtto be a major mediator of the research outcome (e.g., astudy on an antihypertensive therapy or lifestyle changewith a cardiovascular outcome). The recommendationsconstitute a minimum standard for the conduct andreport of each human clinical and epidemiologicalresearch study.
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Norm RC Campbell



The number of observers and the professional backgroundof the observer(s) are indicated (e.g., physician,community health workers, nurse, or research assistant).
  • Those who directly assess blood pressure or thosewho train or teach subjects in blood pressure measurementprotocols must be specifically trained for theblood pressure measurement as part of the qualitycontrol for the research study. This applies to office,home/self, and ambulatory blood pressure assessments.
  • For manual blood pressure assessment, the observer(s)are specifically trained and have passed practical testsfor use of technique and accuracy of assessing bloodpressure by auscultation using a double headedstethoscope.20
  • There is semiannual competency testing of those whodirectly assess blood pressure or those who train orteach subjects in blood pressure measurement protocolswhen indicated in studies of a longer duration.

The observers need to be evaluated, and quality ofperformance needs to be periodically assessed usingstatistical tables to detect bias in recorded measurements.Technician retraining is necessary wheredeficiencies are found.

Technical Aspects
  • The measurement conditions are indicated (e.g., location,position/posture, resting period, or instructionsprovided for home/self or ambulatory measurement).
  • All aspects of patient preparation and blood pressuremeasurement must conform with the publishedguidelines of a national or internationalbody recognized for its work in blood pressuremeasurement.1,2,4-6,21,22 The specific set of technicalrecommendations used in the study must be referencedand all modifications to the recommendedtechniques and procedures disclosed.
  • The blood pressure measurement protocol is providedin sufficient detail so that it can be duplicated preciselyby others (e.g., number of readings recorded,time intervals between readings, criteria for discardingreadings, and number of readings to make theestimation).

Blood Pressure Devices
  • All manual devices must be assessed for calibrationat the start, every 6 months, and end of the study,and the data are to be assessed and reported forterminal digit preference. References are providedfor protocols verifying calibration of manual devices.Mercury devices, if used, must have been servicedbefore the study (e.g., clean columns, and mercury"zeroed").
  • All the semiautomated or automated devices used havepassed accepted international or national validationstandards/protocols (Medaval, http://medaval.org,Updated: 2015. accessed August 17, 2015). Referencesmust be provided (e.g., peer-reviewed publication,government organization verified validation, or publicallyaccessible data) to support the validation of thedevices used.
  • The inflatable bladder dimensions of each cuff sizeused and range of arm circumferences used for eachcuff size are specified. Only upper arm cuffs arerecommended.

  • Blood pressure is assessed using an automated, semiautomated,or manual device for office blood pressure measurement; or an automated device for home/selfor ambulatory blood pressure monitoring.


Recommended Standards for assessing Blood Pressure in Human Research

- Office blood pressure: If blood pressure is assessedin a research/clinical office, multiple blood pressurereadings must be taken and averaged at eachassessment. Office blood pressure evaluation onrepeated occasions (visits) is preferred to establishmore accurately an individual's blood pressurelevel both at baseline and during an intervention.

- Out-of-office blood pressure: It is further preferredthat out-of-office (ambulatory or home/self) bloodpressure be assessed rather than only assessmentsin research/clinical offices. For out-of-officeassessments, it is preferred to use an ambulatoryblood pressure over home/self-monitoring or touse both methods. For ambulatory blood pressuremonitoring, there must be repeated blood pressuremeasurements over a minimum of 24 hoursduring a person's routine day. The ambulatorymonitoring must be performed at baseline andat least once during the intervention. For home/self-blood pressure monitoring, an average of tworeadings in the morning and two readings in theevening conducted on 5 to 7 serial days is recommendedto establish a person's blood pressureboth at baseline and during the intervention.23-26The validity (assessment) of home/self-bloodpressure during an intervention must be assessed(conducted) at least once.

  • Blood pressure in children is preferred to be assessedusing manual devices with auscultation, and interpretedusing blood pressure percentiles/Z-scoresbased on appropriate pediatric normative data.7,27-30

- The use of automated or semiautomated devicesthat have passed internationally accepted validationstandards for children is also acceptable(www.medaval.org/, accessed August 15, 2015).

- Assessment of office blood pressure on severaloccasions/visits is preferred over a single assessmentto establish a child's level of blood pressureboth at baseline and during an intervention.

- In children aged 5 years or over (or a height of120 cm or over), out-of-office blood pressure canbe assessed as a useful addition to assessments inresearch/clinical offices. Out-of-office assessmentsfor children should preferably use an ambulatoryblood pressure monitor.31 There is currentlyinadequate research on home/self-measurementof blood pressure to recommend its use outsideof studies that are designed to further assessthe usefulness of home/self-measurement.32 Forambulatory blood pressure monitoring, there must be repeated blood pressure measurements over aminimum of 24 hours during a child's routine day.The ambulatory monitoring must be performed atbaseline and at least once during the intervention.Appropriate pediatric normative blood pressuredata for ambulatory blood pressure monitoringmust be used for interpretation.33,34 Ambulatoryblood pressure is limited by the very small numberof devices that have been tested according to internationalstandards in children and incompleteevidence on normative data.

  • An upper arm cuff with the length of the cuff'sbladder at least 80% of the arm circumference and thewidth at least 40% of the arm circumference must beused, and the criteria for selecting an appropriatelysized cuff are indicated.


The TRUE recommendations for assessing blood pressureare not intended to impede research on bloodpressure and hypertension in humans but to standardizeand improve the quality and reliability of such research.The recommendations originated from a process todevelop recommended standards for research on dietarysalt where low-quality research was viewed as a majorfactor in creating controversy around lowering dietarysalt. Low-quality assessment of blood pressure wasidentified as having the potential to alter and reduce theassociation between dietary salt and blood pressure. TheTRUE steering and expert committees identified lack ofstandardization of blood pressure measurement and lowquality assessment of blood pressure in human researchas an issue impacting all blood pressure research, andapproved the process to set these recommendations.

The process for developing the TRUE recommendationshad a potential limitation. The recommendationswere based on existing national and international guidelineson how to assess blood pressure and are mainlyfocused on clinical practice.1-8 Many of these processesused extensive literature searches but did not use currentmethods of assessing the quality of evidence or gradingof evidence. A notable exception was the CanadianHypertension Education Program.3 The Canadian recommendationsdid not differ substantively from recommendationsof other processes. New recommendations werenot developed by this process and a literature searchwas not performed. Experts of the TRUE process andexternal experts reviewed the proposed recommendationsto ensure consistency with currently acceptedand published recommendations. Where there was adifference in recommendations between differentguidelines, and a consensus was not achieved, the TRUEprocess did not specify a recommendation to be followed. Hence, the recommendations from this process maynot be as rigorous as those in some clinical guidelines.Therefore, the TRUE recommendations can be viewed asa minimum standard for research studies. It was identifiedthat there is a need for an international process tosystematically review the literature, assess the qualityof studies, and to grade the evidence in setting recommendedstandards for assessing blood pressure.
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Norm RC Campbell

The process for developing the blood pressureassessment recommendations was initiated in January2015 and consensus among the external blood pressuremeasurement experts and the sodium expert committeewas completed in November and December 2015respectively. The process of achieving support from thesteering committee member organizations, several whichhad internal review processes, was complete by August2016. It is recognized that these recommendations shouldbe reviewed and updated with advancement in bloodpressure assessment research.

The introduction of the TRUE recommendationswill require time to allow the research community toadapt. It is suggested that researchers immediatelyapply these recommendations to all research protocolswhere accurate blood pressure assessment is importantto the research results. For journal editors and articlereviewers, it should be expected that research initiatedafter the release of these guidelines adhere to the TRUErecommendations. Further, based on this guidance, atthis time editors and reviewers can ensure the detailedmethods used to assess blood pressure are outlined inappendices of manuscripts. In the meantime, cliniciansand scientist should utilize the TRUE recommendationsin interpreting the validity of past, current, and futureblood pressure research. Specifically, studies with resultsthat are dependent on an accurate assessment of bloodpressure need to be viewed more skeptically where thereis a lack of adherence to recommendations for accurateblood pressure assessment.

It is recognized that innovative research on how tobetter assess blood pressure will test methods that arenot included in these recommendations. Research usingnew methods of assessing blood pressure should comparethe new methods to established methods that incorporatethe TRUE recommendations.

The member organizations and their representativesin the TRUE Consortium* are American Heart Association:Stephen Daniels, British Hypertension Society:Francesco P Cappuccio, Chinese Regional Office of theWorld Hypertension League: Liu Lisheng, HypertensionCanada: Janusz Kaczorowski, International Association of National Public Health Institutes: Antti Jula, InternationalCouncil of Cardiovascular Prevention and Rehabilitation:Alison Atrey, International Society of Hypertension:Rhian Touyz, Agustin Ramirez, InternationalSociety of Nephrology: Ricardo Correa-Rotter, Journalof Clinical Hypertension: Michael Weber, World HealthOrganization Collaborating Centre for populationsalt reduction: Jacqui Webster, Pan American HealthOrganization/ World Health Organization TechnicalAdvisory Group on cardiovascular diseases preventionthrough population wide dietary salt reduction: BrankaLegetic, World Hypertension League: Norm Campbell(Chair), World Stroke Organization: Graeme Hankeywith the World Health Organization (Temo Waqanivalu)as an observing organization. The members ofthe TRUE sodium expert committee are: Drs CherylAnderson, Larry Appel, Norm Campbell (Chair),Mary Cogswell, Nancy Cook, Antti Jula, Mary L'Abbe,Graham MacGregor, Rachael McLean, Doreen Rabi,Mark Woodward, JoAnne Arcand and were supportedby Tej Khalsa, Claire Johnson, Alex Leung, BirinderMangat, and Mark Niebylski. External blood pressureassessment experts who are not part of the TRUE sodiumexpert committee but contributed to this specific set ofrecommendations include Mark Gelfer, Pedro Ordunez,Bruce Alpert, Raj Padwal, Lyne Cloutier, George Stergiou,Eoin O'Brien, Don MacKay, Martin Myers, Joseph Flynn,Janusz Feber, Michael Rakotz, Fleetwood Loustalot, andJanis Dionne. This process was supported by the Heartand Stroke Foundation (Canada), Canadian Institute forHealth Research Chair in Hypertension Prevention andControl and the World Hypertension League.

The TRUE Consortium would like to acknowledge thecontributions of Mark Niebylski, Kimbree Redburn, andAaron Lucko in supporting the TRUE Consortium.

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