ADHERENCE TO LONG-TERM THERAPIES
`
`Evidence for action
`
`World Health Organization 2003
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`

`
`WHO Library Cataloguing-in-Publication Data
`Adherence to long-term therapies: evidence for action.
`1. Patient compliance
`2. Long-term care
`3. Drug therapy – utilization
`4. Chronic disease – therapy
`5. Health behavior
`6. Evidence-based medicine
`I. WHO Adherence to Long Term Therapies Project
`II. Global Adherence Interdisciplinary Network.
`
`ISBN 92 4 154599 2
`
`(NLM classification: W 85)
`
`© World Health Organization 2003
`
`All rights reserved.
`Publications of the World Health Organization can be obtained from Marketing and Dissemination,
`World Health Organization, 20 Avenue Appia, 1211 Geneva 27, Switzerland (tel: +41 22 791 2476;
`fax: +41 22 791 4857; email: bookorders@who.int). Requests for permission to reproduce or translate
`WHO publications – whether for sale or for noncommercial distribution – should be addressed to
`Publications, at the above address (fax: +41 22 791 4806; email: permissions@who.int).
`
`The designations employed and the presentation of the material in this publication do not imply the
`expression of any opinion whatsoever on the part of the World Health Organization concerning the
`legal status of any country, territory, city or area or of its authorities, or concerning the delimitation of
`its frontiers or boundaries. Dotted lines on maps represent approximate border lines for which there
`may not yet be full agreement.
`
`The mention of specific companies or of certain manufacturers’ products does not imply that they
`are endorsed or recommended by the World Health Organization in preference to others of a similar
`nature that are not mentioned. Errors and omissions excepted, the names of proprietary products are
`distinguished by initial capital letters.
`
`The World Health Organization does not warrant that the information contained in this publication
`is complete and correct and shall not be liable for any damages incurred as a result of its use.
`
`Printed in Switzerland.
`
`All correspondence should be sent to the author. Eduardo Sabaté, World Health Organization,
`avenue Appia 20, CH-1211 Geneva 27, Switzerland (sabatee@who.int). Requests for free electronic
`copies (pdf format only) should be sent to: adherence@who.int
`
`

`
`C O N T E N T S
`
`Preface
`Ackowledgement
`Scientific writers
`Introduction
`Take-home messages
`
`Section I – Setting the scene
`
`Chapter I – Defining adherence
`Chapter II – The magnitude of the problem of poor adherence
`Chapter III – How does poor adherence affect policy makers and health managers?
`
`Section II – Improving adherence rates: guidance for countries
`
`Chapter IV – Lessons learned
`Chapter V – Towards the solution
`Chapter VI – How can improved adherence be translated into health
`and economics benefits?
`
`Section III – Disease-specific reviews
`
`Chapter VII – Asthma
`Chapter VIII – Cancer (palliative care)
`Chapter IX – Depression
`Chapter X – Diabetes
`Chapter XI – Epilepsy
`Chapter XII – HIV/AIDS
`Chapter XIII – Hypertension
`Chapter XIV – Tobacco smoking cessation
`Chapter XV – Tuberculosis
`
`Annexes
`
`Annex I – Behavioural mechanisms explaining adherence
`Annex II – Statements by stakeholders
`Annex III – Table of reported factors by condition and dimension
`Annex IV – Table of reported interventions by condition and dimension
`Annex V – Global adherence interdisciplinary network (GAIN)
`
`Where to find a copy of this book
`
`Official designated depositories libraries for WHO publications
`Reference libraries for WHO publications
`WHO official sales agents world wide
`Selected WHO publications of related interest
`A ready-to-use pamphlet for partners willing to promote this book
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`WHO 2003
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`Preface
`
`Over the past few decades we have witnessed several phases in the development of approaches aimed
`at ensuring that patients continue therapy for chronic conditions for long periods of time. Initially the
`patient was thought to be the source of the “problem of compliance”. Later, the role of the providers
`was also addressed. Now we acknowledge that a systems approach is required. The idea of compliance
`is associated too closely with blame, be it of providers or patients and the concept of adherence is a
`better way of capturing the dynamic and complex changes required of many players over long periods
`to maintain optimal health in people with chronic diseases.
`
`This report provides a critical review of what is known about adherence to long-term therapies. This is
`achieved by looking beyond individual diseases. By including communicable diseases such as tuberculo-
`sis and human immunodeficiency virus/acquired immunodeficiency syndrome; mental and neurological
`conditions such as depression and epilepsy; substance dependence (exemplified by smoking cessation);
`as well as hypertension, asthma and palliative care for cancer, a broad range of policy options emerges.
`Furthermore, this broader focus highlights certain common issues that need to be addressed with respect
`to all chronic conditions regardless of their cause. These are primarily related to the way in which health
`systems are structured, financed and operated.
`
`We hope that readers of this report will recognize that simplistic approaches to improving the quality of
`life of people with chronic conditions are not possible. What is required instead, is a deliberative approach
`that starts with reviewing the way health professionals are trained and rewarded, and includes systemati-
`cally tackling the many barriers patients and their families encounter as they strive daily to maintain opti-
`mal health.
`
`This report is intended to make a modest contribution to a much-needed debate about adherence.
`It provides analysis and solutions, it recommends that more research be conducted, but critically
`acknowledges the abundance of what we already know but do not apply. The potential rewards for
`patients and societies of addressing adherence to long-term therapies are large. WHO urges the readers
`of this report to work with us as we make the rewards real.
`
`Derek Yach
`January 2003
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`WHO 2003
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`Acknowledgements
`
`This report was edited by Eduardo Sabaté, WHO Medical Officer responsible for coordinating the WHO
`Adherence to Long-term Therapies Project, Noncommuniclable Diseases department.
`
`Deep appreciation is due to Rafael Bengoa, who envisioned the project and shaped the most crucial
`elements of the report, Derek Yach, who provided consistent support, intellectual stimulation and leader-
`ship to the project and Silvana De Castro, who provided valuable assistance with the many bibliograph-
`ical reviews and with the writing of specific sections of this report.
`
`Special appreciation goes to the scientific writers who provided their ideas and the material for the
`report. Their dedication and voluntary contributions have been central to this work. Thanks are also due
`to all the participants from WHO and the Global Adherence Interdisciplinary Network (GAIN) who by
`their continuous involvement and input during the planning, resource collection and writing phases of
`this project have given breadth and depth to the report.
`
`Special thanks go to Steve Hotz for his intellectual support and hard work in helping to integrate the
`information on behavioural knowledge and its practical implications. Several international professional
`associations, in particular the International Society of Behavioural Medicine, the International Council of
`Nurses, the International Union of Psychological Sciences, the International Pharmaceutical Federation,
`and the World Organization of Family Doctors have played an important role in providing moral sup-
`port and valuable input to the report.
`
`Thanks are also due to Susan Kaplan, who edited the final text, and Tushita Bosonet, who was responsi-
`ble for the artistic design.
`
`The production of this report was made possible through the generous financial support of the gov-
`ernements of United Kingdom, Finland, Netherlands, Norway and Switzerland.
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`Scientific writers
`
`The scientific writers who were invited to contribute to the report are recognized scientists in adherence-
`related issues. Their contributions were made voluntarily and have been incorporated following the
`directions of the editor of the report. All of them signed a Declaration of Interest. They are listed below
`in alphabetical order by topic. (Team leaders are indicated with an asterisk.)
`
`Asthma
`Bender, Bruce • Head • Pediatric Behavioral Health,
`National Jewish Medical and Research Center • USA
`
`Boulet, Louis-Philippe • Professor • Laval University,
`Laval Hospital • Canada
`
`Chaustre, Ismenia • Attending Physician and
`Professor • “JM de los Ríos” Children’s Hospital •
`Venezuela
`
`Rand, Cynthia* • Associate Professor • Johns
`Hopkins University • USA
`
`Weinstein, Andrew • Researcher and Clinical
`Practitioner • Christiana Medical Center • USA
`
`Depression
`Peveler, Robert* • Head • Mental Health Group,
`Community Clinical Sciences Division, School of
`Medicine, University of Southampton • England
`
`Tejada, Maria Luisa • Clinical practitioner • Hospital
`of Nyon • Switzerland
`
`With the active support of the
`WHO-NMH/MSD/Mental and behavioural disorders
`unit
`
`Diabetes
`Karkashian, Christine* • Dean • School of
`Psychology, Latina University • Costa Rica
`
`With the active support of the WHO-NMH/MNC/
`Chronic Respiratory Diseases unit
`
`Schlundt, David • Associate Professor of
`Psychology • Vanderbilt University • USA
`
`Behavioural mechanisms
`Hotz Stephen* • University Research Fellow •
`University of Ottawa • Canada
`
`Kaptein, Ad A. • Head • Psychology unit, Leiden
`University Medical Centre • The Netherlands
`
`Pruitt, Sheri • Director of Behavioral Medicine •
`Permanente Medical Group • USA
`
`Sanchez Sosa, Juan • Professor • National
`University of Mexico • Mexico
`
`Willey, Cynthia • Professor of Pharmacoepidemio-
`logy • University of Rhode Island • USA
`
`Cancer
`De Castro, Silvana* • Technical Officer • Adherence
`Project, Department of Managment of
`Communicable Diseases, WHO • Switzerland
`
`With the active support of the
`WHO-NMH/MNC/Diabetes unit
`
`Epilepsy
`Avanzini, Giuliano • President • International
`League against Epilepsy • Italy
`
`de Boer, Hanneke M. • Global Campaign Co-Chair •
`The International Bureau for Epilepsy/Stichting
`Epilepsie Instellingen Nederland • the Netherlands
`
`De Castro, Silvana* • Technical Officer • Adherence
`Project, Department of Managment of
`Communicable Diseases, WHO • Switzerland
`
`Engel, Jerome Jr • Global Campaign Co-Chair •
`International League against Epilepsy and
`Director of the Seizure Disorder Center, University
`of California at Los Angeles School of Medicine •
`USA
`
`Sabaté, Eduardo • Medical Officer • Adherence
`Project, Department of Managment of
`Communicable Diseases, WHO • Switzerland
`
`With the active support of the WHO-NMH/MNC/
`Program on Cancer Control unit
`
`Lee, Philip • President • International Bureau for
`Epilepsy • Ireland
`
`Sabaté, Eduardo • Medical Officer • Adherence
`Project, Department of Managment of
`Communicable Diseases, WHO • Switzerland
`
`WHO 2003 VIII ❘
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`
`With the active support of the
`WHO-NMH/MSD/Epilepsy unit, the International
`League Against Epilepsy and the International
`Bureau for Epilepsy
`
`Smirnoff, Margaret • Nurse Practitioner • Mount
`Sinai Center • USA
`
`With the active support of the WHO-
`NMH/Tobacco Free Initiative department
`
`Human immunodeficiency virus
`(HIV)/acquired immunodeficiency
`syndrome (AIDS)
`Chesney, Margaret A.* • Professor of Medicine •
`University of California at San Francisco,
`Prevention Sciences Group • USA
`
`Tuberculosis
`Dick, Judy* • Senior Researcher • Medical Research
`Center of South Africa • South Africa
`
`Jaramillo, Ernesto • Medical Officer • Stop TB, WHO
`• Switzerland
`
`Farmer, Paul • Director • Partners in health •
`Harvard University • USA
`
`Maher, Dermot • Medical Officer • Stop TB, WHO
`• Switzerland
`
`Leandre, Fernet • Director • Zanmi Lazante Health
`Care • Haiti
`
`Volmink, Jimmy • Director of Research and
`Analysis • Global Health Council • USA
`
`Malow, Robert • Professor and Director • AIDS
`Prevention Program, Florida International
`University • USA
`
`Starace, Fabrizio • Director • Consultation
`Psychiatry and Behavioural Epidemiology Service,
`Cotugno Hospital • Italy
`
`With the active support of the WHO-HIV/AIDS
`care unit
`
`Hypertension
`Mendis, Shanti* • Coordinator • Cardiovascular
`diseases • WHO-HQ
`
`Salas, Maribel • Senior Researcher • Caro Research
`Institute • USA
`
`Smoking cessation
`De Castro, Silvana • Technical Officer • Adherence
`Project, Department of Managment of
`Communicable Diseases, WHO • Switzerland
`
`Lam, Tai Hing • Professor • Head Department of
`Community Medicine and Behavioural Sciences,
`University of Hong Kong • China
`
`Sabaté, Eduardo* • Medical Officer • Adherence
`Project, Department of Managment of
`Communicable Diseases, WHO • Switzerland
`
`Special topics
`Children and adolescents
`Burkhart, Patricia • Assistant Professor and Nurse
`Researcher • University of Kentucky • USA
`
`With the active support of the
`WHO-FCH/Child and adolescent health unit
`
`Elderly patients
`Di Pollina, Laura • Chief • Clinical Geriatrics,
`Geneva University Hospital • Switzerland
`
`Health Economics
`Kisa, Adnan • Associate Professor • Baskent
`University • Turkey
`
`Nuño, Roberto • Health Economist • Spain
`
`Sabaté, Eduardo* • Medical Officer • Adherence
`Project, Department of Managment of
`Communicable Diseases, WHO • Switzerland
`
`Patients’ perception of illness
`Horne, Rob • Director and Professor of Psychology
`in Health Care • Centre for Health Care Research,
`University of Brighton • England
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`Introduction
`
`Objectives and target audience
`This report is part of the work of the Adherence to Long-term Therapies Project, a global initiative
`launched in 2001 by the Noncommunicable Diseases and Mental Health Cluster of the World Health
`Organization.
`
`The main target audience for this report are policy-makers and health managers who can have an
`impact on national and local policies in ways that will benefit patients, health systems and societies
`with better health outcomes and economic efficiency. This report will also be a useful reference for
`scientists and clinicians in their daily work.
`
`The main objective of the project is to improve worldwide rates of adherence to therapies commonly
`used in treating chronic conditions.
`
`The four objectives of this report are to:
`
`• summarize the existing knowledge on adherence, which will then serve as
`the basis for further policy development;
`
`• increase awareness among policy-makers and health managers about the
`problem of poor rates of adherence that exists worldwide, and its health and
`economic consequences;
`
`• promote discussion of issues related to adherence; and
`
`• provide the basis for policy guidance on adherence for use by individual
`
`• articulating consistent, ethical and evidence-based policy and advocacyposi-
`tions; and
`
`• managing information by assessing trends and comparing performance, set-
`ting the agenda for, and stimulating, research and involvement.
`
`How to read this report
`As this report intends to reach a wide group of professionals, with varied disciplines and roles, the inclusion
`of various topics at different levels of complexity was unavoidable. Also, during the compilation of the
`report, contributions were received from eminent scientists in different fields, who used their own tech-
`nical languages, classifications and definitions when discussing adherence.
`
`For the sake of simplicity, a table has been included for each disease reviewed in section III, showing the
`factors and interventions cited in the text, classified according to the five dimensions proposed by the
`project group and explained later in this report:
`
`–social- and economic-related factors/interventions;
`
`–health system/health care team-related factors/interventions;
`
`–therapy-related factors/interventions;
`
`–condition-related factors/interventions; and
`
`–patient-related factors/interventions.
`
`The section entitled “Take-home messages” summarizes the main findings of this report and indicates
`how readers could make use of them.
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`Section I:
`Setting the scene, discusses the main concepts leading to the definition of adherence and its relevance
`to epidemiology and economics.
`
`Section II:
`Improving adherence rates: guidance for countries, summarizes the lessons learned from the reviews
`studied for this report and puts into context the real impact of adherence on health and economics
`for those who can make a change.
`
`Section III:
`Disease-specific reviews, discusses nine chronic conditions that were reviewed in depth. Readers
`with clinical practice or disease-oriented programmes will find it useful to read the review related
`to their current work. Policy-makers and health managers may prefer to move on to the Annexes.
`
`Annex I:
`Behavioural mechanisms explaining adherence, provides an interesting summary of the existing
`models for explaining people’s behaviour (adherence or nonadherence), and explores the behavioural
`interventions that have been tested for improving adherence rates.
`
`Annex II:
`Statements by stakeholders, looks at the role of the stakeholder in improving adherence as evaluated
`by the stakeholders themselves.
`
`Annexes III and IV:
`Table of reported factors by condition and dimension and Table of reported interventions by condition
`and dimension, provide a summary of all the factors and interventions discussed in this report. These
`tables may be used to look for commonalities among different conditions.
`
`Annexe V:
`Global Adherence Interdisciplinary network (GAIN), lists the members of this network.
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`Take-home messages
`
`Poor adherence to treatment of chronic diseases is a worldwide problem of
`striking magnitude
`Adherence to long-term therapy for chronic illnesses in developed countries averages 50%. In developing
`countries, the rates are even lower. It is undeniable that many patients experience difficulty in following
`treatment recommendations.
`
`The impact of poor adherence grows as the burden of chronic disease grows
`worldwide
`Noncommunicable diseases and mental disorders, human immunodeficiency virus/acquired immuno-
`deficiency syndrome and tuberculosis, together represented 54% of the burden of all diseases world-
`wide in 2001 and will exceed 65% worldwide in 2020. The poor are disproportionately affected.
`
`The consequences of poor adherence to long-term therapies are poor health
`outcomes and increased health care costs
`Poor adherence to long-term therapies severely compromises the effectiveness of treatment making
`this a critical issue in population health both from the perspective of quality of life and of health eco-
`nomics. Interventions aimed at improving adherence would provide a significant positive return on
`investment through primary prevention (of risk factors) and secondary prevention of adverse health
`outcomes.
`
`Improving adherence also enhances patients’ safety
`Because most of the care needed for chronic conditions is based on patient self-management (usually
`requiring complex multi-therapies), use of medical technology for monitoring, and changes in the
`patient’s lifestyle, patients face several potentially life-threatening risks if not appropriately supported
`by the health system.
`
`Adherence is an important modifier of health system effectiveness
`Health outcomes cannot be accurately assessed if they are measured predominantly by resource utilization
`indicators and efficacy of interventions. The population health outcomes predicted by treatment efficacy
`data cannot be achieved unless adherence rates are used to inform planning and project evaluation.
`
`“Increasing the effectiveness of adherence interventions may have a far
`greater impact on the health of the population than any improvement in
`specific medical treatments”1
`Studies consistently find significant cost-savings and increases in the effectiveness of health interven-
`tions that are attributable to low-cost interventions for improving adherence. Without a system that
`addresses the determinants of adherence, advances in biomedical technology will fail to realize their
`potential to reduce the burden of chronic illness. Access to medications is necessary but insufficient in
`itself for the successful treatment of disease.
`
`Health systems must evolve to meet new challenges
`In developed countries, the epidemiological shift in disease burden from acute to chronic diseases over
`the past 50 years has rendered acute care models of health service delivery inadequate to address the
`health needs of the population. In developing countries, this shift is occurring at a much faster rate.
`
`1Haynes RB. Interventions for helping patients to follow prescriptions for medications.
`Cochrane Database of Systematic Reviews, 2001, Issue 1.
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`Patients need to be supported, not blamed
`Despite evidence to the contrary, there continues to be a tendency to focus on patient-related factors
`as the causes of problems with adherence, to the relative neglect of provider and health system-related
`determinants. These latter factors, which make up the health care environment in which patients
`receive care, have a major effect on adherence.
`
`Adherence is simultaneously influenced by several factors
`The ability of patients to follow treatment plans in an optimal manner is frequently compromised by
`more than one barrier, usually related to different aspects of the problem. These include: the social and
`economic factors, the health care team/system, the characteristics of the disease, disease therapies and
`patient-related factors. Solving the problems related to each of these factors is necessary if patients’
`adherence to therapies is to be improved.
`
`Patient-tailored interventions are required
`There is no single intervention strategy, or package of strategies that has been shown to be effective
`across all patients, conditions and settings. Consequently, interventions that target adherence must be
`tailored to the particular illness-related demands experienced by the patient. To accomplish this, health
`systems and providers need to develop means of accurately assessing not only adherence, but also
`those factors that influence it.
`
`Adherence is a dynamic process that needs to be followed up
`Improving adherence requires a continuous and dynamic process. Recent research in the behavioural
`sciences has revealed that the patient population can be segmented according to level-of-readiness to
`follow health recommendations. The lack of a match between patient readiness and the practitioner’s
`attempts at intervention means that treatments are frequently prescribed to patients who are not ready
`to follow them. Health care providers should be able to assess the patient’s readiness to adhere, provide
`advice on how to do it, and follow up the patient’s progress at every contact.
`
`Health professionals need to be trained in adherence
`Health providers can have a significant impact by assessing risk of nonadherence and delivering inter-
`ventions to optimize adherence. To make this practice a reality, practitioners must have access to specif-
`ic training in adherence management, and the systems in which they work must design and support
`delivery systems that respect this objective. For empowering health professionals an “adherence coun-
`selling toolkit” adaptable to different socioeconomic settings is urgently needed. Such training needs
`to simultaneously address three topics: knowledge (information on adherence), thinking (the clinical
`decision-making process) and action (behavioural tools for health professionals).
`
`Family, community and patients’ organizations: a key factor for success in
`improving adherence
`For the effective provision of care for chronic conditions, it is necessary that the patient, the family and
`the community who support him or her all play an active role. Social support, i.e. informal or formal sup-
`port received by patients from other members of their community, has been consistently reported as
`an important factor affecting health outcomes and behaviours. There is substantial evidence that peer
`support among patients can improve adherence to therapy while reducing the amount of time devoted
`by the health professionals to the care of chronic conditions.
`
`A multidisciplinary approach towards adherence is needed
`A stronger commitment to a multidisciplinary approach is needed to make progress in this area.
`This will require coordinated action from health professionals, researchers, health planners and policy-
`makers.
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`Section I
`
`S E C T I O N
`
`I
`
`Setting the scene
`
`

`
`Chapter I
`
`C H A P T E R
`
`I
`
`Defining adherence
`
`1. What is adherence?
`
`3
`
`2. The state-of-the-art measurement 4
`
`3. References 5
`
`1. What is adherence?
`
`Although most research has focused on adherence to medication, adherence also encompasses numer-
`ous health-related behaviours that extend beyond taking prescribed pharmaceuticals. The participants
`at the WHO Adherence meeting in June 2001 (1) concluded that defining adherence as “the extent to
`which the patient follows medical instructions” was a helpful starting point. However, the term “med-
`ical” was felt to be insufficient in describing the range of interventions used to treat chronic diseases.
`Furthermore, the term “instructions” implies that the patient is a passive, acquiescent recipient of expert
`advice as opposed to an active collaborator in the treatment process.
`
`In particular, it was recognized during the meeting that adherence to any regimen reflects behaviour
`of one type or another. Seeking medical attention, filling prescriptions, taking medication appropriately,
`obtaining immunizations, attending follow-up appointments, and executing behavioural modifications
`that address personal hygiene, self-management of asthma or diabetes, smoking, contraception, risky
`sexual behaviours, unhealthy diet and insufficient levels of physical activity are all examples of thera-
`peutic behaviours.
`
`The participants at the meeting also noted that the relationship between the patient and the health
`care provider (be it physician, nurse or other health practitioner) must be a partnership that draws on
`the abilities of each. The literature has identified the quality of the treatment relationship as being an
`important determinant of adherence. Effective treatment relationships are characterized by an atmos-
`phere in which alternative therapeutic means are explored, the regimen is negotiated, adherence is
`discussed, and follow-up is planned.
`
`The adherence project has adopted the following definition of adherence to long-term therapy, a
`merged version of the definitions of Haynes (2) and Rand (3):
`
`the extent to which a person’s behaviour – taking medication, following a diet,
`
`and/or executing lifestyle changes, corresponds with agreed recommendations
`
`from a health care provider.
`
`

`
`Strong emphasis was placed on the need to differentiate adherence from compliance. The main differ-
`ence is that adherence requires the patient’s agreement to the recommendations. We believe that
`patients should be active partners with health professionals in their own care and that good communi-
`cation between patient and health professional is a must for an effective clinical practice.
`
`In most of the studies reviewed here, it was not clear whether or not the “patient’s previous agreement
`to recommendations” was taken into consideration. Therefore, the terms used by the original authors
`for describing compliance or adherence behaviours have been reported here.
`
`A clear distinction between the concepts of acute as opposed to chronic, and communicable (infectious)
`as opposed to noncommunicable, diseases must also be established in order to understand the type of
`care needed. Chronic conditions, such as human immunodeficiency virus (HIV), acquired immunodefi-
`ciency syndrome (AIDS) and tuberculosis, may be infectious in origin and will need the same kind of
`care as many other chronic noncommunicable diseases such as hypertension, diabetes and depression.
`
`The adherence project has adopted the following definition of chronic diseases:
`
`“Diseases which have one or more of the following characteristics: they are
`
`permanent, leave residual disability, are caused by nonreversible pathological
`
`alteration, require special training of the patient for rehabilitation, or may be
`
`expected to require a long period of supervision, observation or care” (4).
`
`2. The state-of-the-art measurement
`
`Accurate assessment of adherence behaviour is necessary for effective and efficient treatment planning,
`and for ensuring that changes in health outcomes can be attributed to the recommended regimen. In
`addition, decisions to change recommendations, medications, and/or communication style in order to
`promote patient participation depend on valid and reliable measurement of the adherence construct.
`Indisputably, there is no “gold standard” for measuring adherence behaviour (5,6) and the use of a vari-
`ety of strategies has been reported in the literature.
`
`One measurement approach is to ask providers and patients for their subjective ratings of adherence
`behaviour. However, when providers rate the degree to which patients follow their recommendations
`they overestimate adherence (7,8). The analysis of patients’ subjective reports has been problematic as
`well. Patients who reveal they have not followed treatment advice tend to describe their behaviour
`accurately (9), whereas patients who deny their failure to follow recommendations report their behav-
`iour inaccurately (10). Other subjective means for measuring adherence include standardized, patient-
`administered questionnaires (11). Typical strategies have assessed global patient characteristics or “per-
`sonality” traits, but these have proven to be poor predictors of adherence behaviour (6). There are no
`stable (i.e. trait) factors that reliably predict adherence. However, questionnaires that assess specific
`behaviours that relate to specific medical recommendations (e.g. food frequency questionnaires (12) for
`measuring eating behaviour and improving the management of obesity) may be better predictors of
`adherence behaviour (13).
`
`Although objective strategies may initially appear to be an improvement over subjective approaches,
`each has drawbacks in the assessment of adherence behaviours. Remaining dosage units (e.g. tablets)
`can be counted at clinic visits; however, counting inaccuracies are common and typically result in over-
`estimation of adherence behaviour (14), and important information (e.g. timing of dosage and patterns
`of missed dosages) is not captured using this strategy. A recent innovation is the electronic monitoring
`device (medication event monitoring system (MEMS)) which records the time and date when a medica-
`tion container was opened, thus better describing the way patients take their medications (9).
`
`WHO 2003
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`4 ❘
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`

`
`Unfortunately, the expense of these devices precludes their widespread use. Pharmacy databases can
`be used to check when prescriptions are initially filled, refilled over time, and prematurely discontinued.
`One problem with this approach is that obtaining the medicine does not ensure its use. Also, such infor-
`mation can be incomplete because patients may use more than one pharmacy or data may not be rou-
`tinely captured.
`
`Independently of the measurement technique used, thresholds defining “good” and “bad” adherence
`are widely used despite the lack of evidence to support them. In practice,“good” and “bad” adherence
`might not really exist because the dose–response phenomenon is a continuum function.
`
`Although dose–response curves are difficult to construct for real-life situations, where dosage, timing
`and others variables might be different from those tested in clinical trials, they are needed if sound policy
`decisions are to be made when defining operational adherence thresholds for different therapies.
`
`Biochemical measurement is a third approach for assessing adherence behaviours. Non-toxic biological
`markers can be added to medications and their presence in blood or urine can provide evidence that a
`patient recently received a dose of the medication under examination. This assessment strategy is not
`without drawbacks as findings can be misleading and are influenced by a variety of individual factors
`including diet, absorption and rate of excretion (15).
`
`In summary, measurement of adherence provides useful information that outcome-monitoring alone
`cannot provide, but it remains only