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In order to identify the predominantly used terms in the medical and nursing literature, a broad search of Medline via PubMed and the Cumulative Index of Nursing and Allied Literature (CINAHL) via EBSCO was carried out in January 2015. As search terms, in PubMed, the MeSH-terms patient compliance and medication adherence were used, together with the terms medication concordance and medication persistence, for which no MeSH- terms exist. In CINAHL, only compliance is indexed as patient compliance as a Subject Term Heading, the analogue to MeSH terms, and therefore all other terms were searched as indicated in Table 2. The numbers of hits provided by this search are also shown in Table 2.

Search Terms Number of Hits

PubMed CINAHL

Patient compliance 74,276 21,881

Medication adherence 16,199 3,204

Medication concordance 780 50

Medication persistence 16,828 159

Table 2: Predominantly used terms in medical and nursing literature

This search reveals that compliance is by far the most commonly used term in this context. The high number of hits in the search for medication

persistence in Pub Med is most likely due to the PubMed indexing policy, which integrates articles on persistence under compliance and adherence, as the screening of hits indicates.

2.3 Development of Terminology

Insights into the development of compliance and adherence over the past 50 years were gained when the PubMed search described above was limited to a period of five years. This search showed a continuing increase in the use of compliance, but also a strong increase in adherence, which currently

Figure 2: Comparison of the development of compliance vs. adherence

Both searches reveal existing interest in the issue, but also illustrate a shift in terminology from compliance to adherence for the description of patient behaviour. Despite past and current discussions, compliance still dominates; however, according to the results of the second search, adherence has slowly gained importance, as Vrijens et al. (2012) also observe. These results, however, are not to be overestimated, as it is likely that these results include multiple duplicates, with many references including both compliance and adherence as key words. A similar search in the future may generate different results as terminology continues to change.

2.4 Comparison of Terms

As was illustrated in Table 1, terms referring to taking or not taking

medication as prescribed have somewhat general definitions. This section discusses each term, including commonalities and differences with others.

0 5000 10000 15000 20000 25000

2.4.1 Compliance

The term first introduced in the 1970s to describe patients‘ behaviour in regard to medication-taking was compliance (Lehane & McCarthy 2009). The most-cited, and landmark, definition of compliance is by Sackett & Haynes (1976): “the extent to which the patients’ behaviour […] coincides with medical or healthcare advice” (p.2). The etymological roots of compliance derive from the Latin verb complere (to fulfil) that is used in the sense of obedience but may also connote surrender (OED 2015a).

Both the classic Latin meaning of compliance and the above definition render the patient a follower of instructions rather than a responsible part of the treatment process. It also incorporates a paternalistic relationship between the healthcare professional and the patient, with the former giving advice and the latter obliged to follow. From this perspective, the responsibility of

medication lies exclusively with the patient, and potential other barriers to medication-taking need not be taken into account. Consequently, compliance applies primarily to negative aspects of patients' behaviour (Hobden 2006) in both English and German, where Compliance and Incompliance (non-

compliance) have been introduced as loan words.

Judging a patient as being incompliant in German has extremely negative connotations, similar to labelling the respective patient ‘difficult’ or even ‘bad’. Moreover, non-compliance or “personal history of noncompliance with

medical treatment and regimen” (World Health Organization 2012a, no page) represents a medical diagnosis in the current version of the International Classification of Diseases (ICD) as a subgroup of “personal history of risk- factors, not elsewhere classified” (World Health Organization 2012b). Even a single diagnosis as non-compliant may cause serious problems for a patient, as this is likely to remain in the medical record for a long time. Consequently, the concept has been redefined to reflect a more patient-centred approach (Kyngäs et al. 2000; Ingram 2009), leading to the emergence of adherence around the year 2000.

2.4.2 Adherence

The replacement of compliance with adherence was driven by three main considerations that paralleled a shift in the relationship between healthcare provider and patient. First, a more neutral and less judgmental term than compliance was needed (Fraser 2010). Secondly, reflection of a patient- oriented approach, rather than a paternalistic relationship, was proposed (Vermeire et al. 2001). Lastly, a new term would emphasise the responsibility of the patient in the medication-taking process (Tilson 2004).

Like compliance, adherence has Latin roots, with adhaerere (to stick to) meaning “to believe in and follow the practices of” something (OED 2015b). This supports an autonomous patient who must believe in the necessity of the medication before following the prescribed regimen. Although the use of adherence has risen considerably in the international literature in recent years (Figure 2) and a direct German translation (Adhärenz) is available, the term is not yet integrated into the medical discourse in Germany.

Despite a frequent emphasis on the fundamental advancement of the

concept, definitions of adherence differ considerably (Bissonnette 2008). This is visible in the two most commonly cited definitions. The best-known

definition has been shaped by the World Health Organization (WHO) and defines adherence as: “the extent to which a person’s behaviour […] corresponds with agreed recommendations from a health care provider” (Sabaté 2003, p. 3). In contrast, in a Cochrane review on interventions for enhancing medication adherence, Haynes et al. (2008) use the following definition: “adherence can be defined as the extent to which patients follow the instructions they are given for prescribed treatments” (p. 3).

Both definitions intend to represent a non-judgemental, less paternalistic relationship between prescriber and patient, and to value the patient’s role in medication-taking and decision-making processes. However, the Haynes et al. (2008) definition retains similarities with the Sacket and Haynes (1976) definition of compliance, even sharpening the tone by replacing the verb ‘to coincide’ with ‘to follow’. While ‘to coincide’ means “to be in agreement” (OED 2015c), ‘to follow’ can be defined as “to accept the authority or example of” (OED 2015d). This is also reflected in the shift from ‘advice’ to ‘instruction.’ In contrast, the WHO (2003) definition adds the term ‘agreed’, emphasising the patient’s active role and thus changing the underlying concept.

A different approach was taken by Fine et al. (2009), who defined non-

adherence as “deviation from the prescribed medication regimen sufficient to influence adversely the regimen’s intended effect” (Fine et al. 2009, p. 36). This definition differs from previously on two points. First, by defining the problem, rather than the goal, it avoids distributing responsibility, and the use of ‘deviation’ employs a relatively neutral point of view. Secondly, this

definition incorporates a previously neglected issue, which is the possible adverse consequences of the behaviour.

2.4.3 Concordance

A further development of the terminology was suggested in the 1990s by the RPSGB, who introduced the term concordance to emphasise the need for patient-centred communication (Marinker et al. 1997; cited in Cushing & Metcalfe 2007). Concordance can be defined as:

agreement between the patient and healthcare professional, reached after negotiation that respects the beliefs and wishes of the patient in determining whether, when and how their medicine is taken, and [in which] the primacy of the patient’s decision [is recognised] (p. 1049).

This definition, however, illustrates that the term is not synonymous with adherence or compliance (Horne et al. 2005), as it does not describe the process of medication-taking but rather aims to represent a “new way of consulting” (Hobden 2006, p. 257) between the parties involved. Literally meaning “being one of heart or mind” (OED 2015e), concordance can be traced back to its Latin etymological roots: the word concordantia consists of two parts, con, together, and cor, heart (Kluge & Seebold 2001). The

awareness concordance differs from compliance and adherence may be why the term is predominantly used in the UK (Horne et al. 2005). In the UK, however, concordance is often misleadingly used as a replacement for adherence.

2.4.4 Persistence

The last term describing medication-taking behaviour is persistence, defined as “the length of time between initiation and the last dose, which immediately precedes discontinuation [of a medication]” (Vrijens et al. 2012, p. 696). Persistence is derived from the French verb persister (OED 2015f), to continue, emphasising its time aspect. Persistence, therefore, cannot be used synonymously with compliance or adherence, but rather describes the time-period over which medication is continued, regardless of what causes the medication-taking (Vrijens et al. 2012).