COMMENTARY

What is patient adherence? A terminology overview

Rana Ahmed • Parisa Aslani

� Koninklijke Nederlandse Maatschappij ter bevordering der Pharmacie 2013

Abstract It is well known that patient adherence to

appropriately prescribed medications is essential for treat-

ment efficacy and positive therapeutic outcomes. It is also

understood that patients who are prescribed medications do

not necessarily take them as prescribed. Indeed, variation

in patients’ medication-taking is an age old conundrum

which remains the focus of much interest amongst

researchers and clinicians owing to its far-reaching con-

sequences. Despite the extensive adherence-related

research over the last four decades and a recent surge in

this field, there remains a lack of uniformity in the termi-

nology used to describe adherence and its related concepts.

In turn, it is often difficult to conduct comparisons between

adherence-related studies, which may be associated with

the non-cumulative nature of work in this field. The pur-

pose of this commentary is to provide an overview of key

terminology relating to the field of adherence research.

Keywords Concordance � Medication adherence �Patient compliance � Persistence � Terminology

Impact of Findings on Practice

• There are several commonly used adherence-related

terms in the literature, with apparent differences

between these terms.

• The description of the adherence related terminology

should assist clinicians in interpreting the findings of

research published in this field.

• There is a need for consistency in the adherence-related

terms used to allow for comparison of research in this

area.

Introduction

Patient deviations from prescribed medication regimens

were first noted by Hippocrates (460–370 BC) who gave an

accompanying warning to physicians that patients may lie

about their medication-taking [1]. Since these early

accounts, the area of patient adherence has become the

focus of significant interest amongst clinicians and

researchers [2]. It is now well-established that adherence to

appropriately prescribed medication regimens improves

patient safety, health outcomes and quality of life [3, 4].

Comparatively, poor adherence is associated with treat-

ment inefficacy, increased patient morbidity and mortality

as well as increased healthcare costs [5, 6]. It is estimated

that approximately 50 % of patients with chronic illnesses

are non-adherent to their medication regimens [2]. In light

of its prevalence and far-reaching consequences, it comes

as no surprise that medication adherence is increasingly

becoming recognised as a prominent challenge to clini-

cians, researchers and policymakers [7].

To address this challenge, a surge in research over recent

years has helped elucidate the extent, causes and conse-

quences of patient non-adherence across a variety of health

conditions. Despite this progress, some argue that adher-

ence-related research is fragmented [8] and that it is often

difficult to draw meaningful comparisons between studies,

even between those relating to the same medical condition.

This has been associated with a lack of uniformity in how

adherence and its related concepts are defined and measured

R. Ahmed � P. Aslani (&)

The University of Sydney, Room N502, Pharmacy Building

(A15), Sydney, NSW 2006, Australia

e-mail: parisa.aslani@sydney.edu.au

123

Int J Clin Pharm (2014) 36:4–7

DOI 10.1007/s11096-013-9856-y

in the literature [7–9]. In this way, a patient who is considered

to be adherent in one study may not necessarily satisfy the

adherence criteria of another study meaning that research

implications are often non-generalizable in these instances.

Consequently, contributions to this field are often viewed to

be non-cumulative as they often reinvent, rather than build

upon, existing investigative approaches and definitions [8].

The observed lack of investigative standardisation

amongst adherence-related literature is perhaps a testament

to the inherent complexity of this field of research.

Adherence as a term is used to describe a range of varia-

tions in the medication-taking behaviours of diverse pop-

ulations and relating to disparate disease states [10].

Therefore, not only are differences in adherence definitions

and measurement expected in the literature, but so too are

variations in the terminology used to describe deviations

from prescribed medication regimens. This is reflected in

the variety of terms which have been associated with

adherence over time [11], including compliance, obedi-

ence, observance, acceptance, conformity and co-operation

[10]. Therefore in order to assess the appropriateness,

validity and applicability of research findings, it is impor-

tant to recognize the unique characteristics of these terms

and to understand why the taxonomy of adherence-related

terms and key concepts has evolved over time. It is

important to note that some of these terms are more com-

monly used than others, therefore the purpose of this

commentary is to provide an overview of key terminology

and concepts relating to the field of patient adherence.

Compliance

Compliance was first coined in the 1970s and it was used to

describe a quantifiable parameter of ‘‘the extent to which a

patient’s behaviour (in terms of taking medications, fol-

lowing diets or executing other lifestyle changes) coincides

with the clinical prescription’’ [12]. Despite its widespread

use throughout adherence-related literature, this conceptu-

alisation has been criticised for its paternalistic undertones

and negative implication that patients are expected to

passively follow doctors’ orders [2, 13]. Indeed, this lack of

recognition of patient views regarding their medication-

taking behaviours persisted throughout early literature

since the introduction of ‘patient compliance’ as a Medical

Subject Heading (MeSH) in 1975 [9].

However, as patients’ roles in treatment management

became the focus of research over time, the problematic

nature of the term compliance within this context became

apparent [14]. This is not only owing to the term’s negative

connotations regarding power inequity between clinicians

and their patients, but also because if we consider compli-

ance from the perspective of patients following through with

decisions they have made themselves, then the term becomes

irrelevant and meaningless [15]. In turn, with greater rec-

ognition of patient perspectives about their medication use

came a corresponding decline in the use of the term com-

pliance and its replacement with terms that better illustrate

patients’ involvement in their healthcare [16].

Adherence

The introduction of ‘medication adherence’ as a MeSH term

in 2009 [9] represented a significant paradigm shift towards

recognising patients as key players in their healthcare [16].

As defined by the World Health Organization, adherence is

‘‘the extent to which a person’s behaviour- taking medica-

tion, following a diet and/or executing lifestyle changes,

corresponds with agreed recommendations from a health-

care provider’’ [2]. Therefore, the validity of the definition

and its operationalization in research and clinical practice

hinges upon the proviso that patient and clinician agreement

about the course of treatment is reached in the first instance.

In addressing the need for patient involvement in treatment

decisions, this definition can be viewed to supersede the

concept of compliance and is currently favoured by many

experts in the field [7].

Adherence as a construct is multi-faceted, founded upon

patients’ understanding of their illness severity, their belief

in the efficacy of a particular treatment and in their ability

to control their symptoms by utilising this treatment [17].

To better understand the scope of adherence as a term, it is

useful to examine its three key components: initiation;

implementation; and discontinuation as proposed by the

Ascertaining Barriers for Compliance (ABC) project team

[9, 18]. Initiation is used to describe the first occasion that a

patient takes a dose of a medication after it has been pre-

scribed and is therefore, an inherently discontinuous action

[9]. Comparatively, implementation is a continuous action

representing the extent to which a patient’s dosing corre-

sponds to the dosing, administration frequency and timing

of that prescribed [9, 17]. This is determined for the

duration of time spanning from the date of initiation until

the date of the final dose of the medication. This final dose

falls within the definition of discontinuation, which marks

the end of therapy as indicated by the omission of the next

prescribed dose and cessation of doses thereafter [9].

Persistence

The term persistence is understood to reflect treatment

continuity, defined as the duration of time between therapy

initiation to its discontinuation [9, 17]. Persistence is often

used interchangeably with the term adherence in the

Int J Clin Pharm (2014) 36:4–7 5

123

literature, however they are at times two mutually exclu-

sive constructs. A patient who is considered to be persistent

with their prescribed medication does not necessarily also

qualify as an adherent patient. For example, a patient who

completes a course of antibiotics within the agreed time-

frame specified by the prescriber would be considered to be

persistent. However, if during this time, the patient’s

implementation of the treatment varied to that agreed upon

with the prescriber (e.g. wrong dose consumed or dose

consumed at the wrong time), they would not be considered

to be adherent. Some argue that it is simpler to understand

adherence as the extent to which a patient takes their

medication as prescribed for the duration of time that they

are persistent with their treatment [19].

Concordance and patient-centred care

Whereas compliance, adherence and persistence all repre-

sent quantifiable parameters related to patients’ medica-

tion-taking behaviours, concordance pertains to the

relationship between clinicians and their patients in

reaching shared treatment decisions [7]. This concept was

first introduced by the Pharmaceutical Society of Great

Britain in 1997 as a model of ‘‘shared decision-making and

consensual agreement between doctors and patients as

equal parties’’ [15]. Shared decision-making can be defined

as the joint decisions made by clinicians and patients once

available evidence and patient opinions have been con-

sidered [16]. In this way, concordance is seen to represent a

significant shift from the paternalistic clinician-patient

relationship where patients were expected to passively

follow doctors’ orders, to a more egalitarian one where

patients are seen to ‘‘have enough knowledge to participate

as partners’’ [7] and to adopt a more active role in decisions

pertaining to their treatment. By encouraging patients to

participate as equals during consultations, concordance is

said to foster informed decision-making and strengthen

partnerships with clinicians, allowing open discussion

about treatment options and consensual agreement about

the course of treatment to be reached [20].

Patient-centred care (PCC) is a measure of the quality of

health care [21] and encompasses the shared decision-

making attributes underpinning concordance [7]. It is

defined as ‘‘a partnership among practitioners [and]

patients…to ensure that decisions respect patients’ wants,

needs, and preferences and that patients have the education

and support they require to make decisions and participate

in their own care’’ [22]. This stipulates that the clinician

educates patients about their treatment options to assist

them in arriving at a treatment decision while at the same

time taking their beliefs and preferences into consideration.

Conclusions

Differences in how adherence-related terms and concepts are

defined in the literature and their evolution over time often

make it difficult to draw meaningful comparisons between

studies. This is a reflection of the inherent complexity asso-

ciated with the phenomenon of patient adherence. To provide

some clarity regarding these definitions, we have provided an

overview of key terminology and concepts relating to patient

adherence. However, it is still essential that researchers and

clinicians refer to the specific definitions of adherence-related

measures used in individual studies until more standardisation

of terminology in this field is witnessed.

Funding None.

Conflicts of interest None.

References

1. Adams F. Genuine works of Hippocrates. Melbourne: Krieger

Publishing; 1972.

2. World Health Organization. Adherence to long-term therapies:

evidence for action. Geneva: World Health Organization; 2003.

3. Fredericks EM, Magee JC, Opipari-Arrigan L, Shieck V, Well A,

Lopez MJ. Adherence and health-related quality of life in ado-

lescent liver transplant recipients. Pediatr Transplant.

2008;12(3):289–99.

4. Drotar D, Greenley RN, Demeter CA, et al. Adherence to phar-

macological treatment for juvenile bipolar disorder. J Am Acad

Child Adol Psychiatry. 2007;46(7):831–9.

5. Buckley P. Adherence to mental health treatment. New York:

Oxford University Press; 2009.

6. Osterberg L, Blaschke T. Adherence to medication. N Engl J

Med. 2005;353(5):487–97.

7. Lehane E, Mccarthy G. Medication non-adherence–exploring the

conceptual mire. Int J Nurs Pract. 2009;15(1):25–31.

8. Chacko A, Newcorn JH, Feirsen N, Uderman JZ. Improving

medication adherence in chronic pediatric health conditions: a

focus on ADHD in youth. Curr Pharm Des.

2010;16(22):2416–23.

9. Vrijens B, De Geest S, Hughes DA, et al. A new taxonomy for

describing and defining adherence to medications. Brit J Clin

Pharm. 2012;73(5):691–705.

10. Bissonnette JM. Adherence: a concept analysis. J Adv Nurs.

2008;63(6):634–43.

11. Blackburn DF, Swidrovich J, Lemstra M. Non-adherence in type

2 diabetes: practical considerations for interpreting the literature.

Patient Prefer Adherence. 2013;7:183–9.

12. Sackett DL, Haynes RB. Compliance with therapeutic regimens.

Baltimore: The Johns Hopkins University Press; 1976.

13. Hughes CM. Medication non-adherence in the elderly: how big is

the problem? Drugs Aging. 2004;21:793–811.

14. Blackwell B. From compliance to alliance. A quarter century of

research. Neth J Med. 1996;48:140–9.

15. Segal JZ. Compliance to concordance: a critical view. J Med

Humanit. 2007;28:81–96.

16. National Heart Foundation of Australia. Improving adherence in

cardiovascular care. A toolkit for health professionals. Mel-

bourne: National Heart Foundation of Australia; 2011.

6 Int J Clin Pharm (2014) 36:4–7

123

17. Cramer JA, Roy A, Burrell A, et al. Medication compliance and

persistence: terminology and definitions. Value Health. 2008;

11(1):44–7.

18. Ascertaining barriers for compliance (ABC) project team. ABC

project. [Internet]. [Place unknown]: ABC project; c2010–2012

(2013). Available from: http://abcproject.eu/.

19. Caisley H, Muller U. Adherence to medication in adults with

attention deficit hyperactivity disorder and pro re nata dosing of

psychostimulants: a systematic review. Eur Psychiatry. 2012;

27(5):343–9.

20. Nunes V, Neilson J, O’Flynn N, et al. Clinical guidelines and

evidence review for medicines adherence: involving patients in

decisions about prescribed medicines and supporting adherence.

London: National Collaborating Centre for Primary Care and

Royal College of General Practitioners; 2009.

21. Robinson JH, Callister LC, Berry JA, Dearing KA. Patient-cen-

tered care and adherence: definitions and applications to improve

outcomes. J Am Acad Nurs Pract. 2008;20(12):600–7.

22. Institute of Medicine. Envisioning the national health care quality

report. [Internet]. Washington D.C. (USA): Institute of Medicine;

c2013 (2013). Available from: http://www.nap.edu/openbook.

php?record_id=10073&page=7.

Int J Clin Pharm (2014) 36:4–7 7

123