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The Psychometric Properties and Practicability of Self-Report Instruments to Identify Medication Nonadherence in Adult Transplant Patients: A Systematic Review

Dobbels, Fabienne1,8; Berben, Lut2; De Geest, Sabina1,2; Drent, Gerda3; Lennerling, Annette4; Whittaker, Clare5; Kugler, Christiane6the Transplant360 Task Force

doi: 10.1097/TP.0b013e3181e346cd
Clinical and Translational Research

Introduction. Nonadherence to immunosuppressive therapy is recognized as a key prognostic indicator for poor posttransplantation long-term outcomes. Several methods aiming to measure medication nonadherence have been suggested in the literature. Although combining measurement methods is regarded as the gold standard for measuring nonadherence, self-report is generally considered a central component of adherence assessment. However, no systematic review currently exists to determine which instrument(s) are most appropriate for use in transplant populations.

Methodology. The transplant360 Task Force first performed a survey of the self-report adherence instruments currently used in European centers. Next, a systematic literature review of self-report instruments assessing medication adherence in chronically ill patients was conducted. Self-report instruments were evaluated to assess those which were: (a) short and easy to score; (b) assessed both the taking and timing of medication intake; and (c) had established reliability and validity.

Results. Fourteen instruments were identified from our survey of European centers, of which the Basel Assessment of Adherence Scale for Immunosuppressives met the aforementioned criteria. The systematic review found 20 self-report instruments, of which only two qualified for use in transplantation, that is, the Brief Antiretroviral Adherence Index and the Medication Adherence Self-Report Inventory.

Discussion. The three selected self-report scales may assist transplant professionals in detecting nonadherence. However, these scales were only validated in patients with HIV. Although HIV shares similar characteristics with transplantation, including the importance of taking and timing of medication, further validation in transplant populations is required.

1Department of Public Health, Katholieke Universiteit Leuven, Centre for Health Services and Nursing Research and Heart Transplantation Programme, Leuven, Belgium.

2Institute of Nursing Science, University of Basel, Basel, Switzerland.

3Department of Gastroenterology and Hepatology, University Hospital Groningen, Groningen, The Netherlands.

4Transplant Institute, Sahlgrenska University Hospital, Gothenburg, Sweden.

5Department of Transplantation, The Royal London Hospital, Whitechapel, London, United Kingdom.

6Integrated Research and Treatment Centre, Hannover Medical School, Hannover, Germany.

7Members of the transplant360 Task Force (see Appendix to this article).

Medical writing support in the preparation of this manuscript was provided by Choice Pharma and funded by Astellas Pharma Europe Ltd.

All authors receive remuneration from Astellas Pharma Europe Ltd. for their attendance at Task Force meetings. There are no further conflicts of interest to declare.

8Address correspondence to: Fabienne Dobbels, Ph.D., Katholieke Universiteit Leuven, Centre for Health Services and Nursing Research and Heart Transplantation Programme, Kapucijnenvoer 35/4, B-3000 Leuven, Belgium.

E-mail: fabienne.dobbels@med.kuleuven.be

F.D. participated in review design, performing the review, writing the article, and analysis of findings; L.B. participated in review design and reviewing the article; S.D.G. participated in review design and reviewing the article; G.D. participated in review design and reviewing the article; A.L. participated in review design and reviewing the article; C.W. participated in review design and reviewing the article; C.K. participated in review design, performing the review, and reviewing the article; and the members of the transplant360 Task Force participated in reviewing the article.

Received 18 January 2010. Revision requested 9 February 2010.

Accepted 15 April 2010.

Transplant360 was founded in 2008, with the objective of bringing together key members of the European transplant community, including researchers, clinicians and transplant recipients (The Task Force members are listed in the Appendix), to develop a program of educational initiatives that will support long-term improvements in posttransplant patient management (www.transplant360.com). This initiative originated from the observation that nonadherence to the prescribed medication regimen is a significant problem after transplantation.

A recent meta-analysis found that the prevalence of nonadherence to immunosuppressants was 22.6 cases per 100 patients per year across organ transplant groups (1). The detrimental effect of nonadherence on short- and long-term transplant outcomes is substantial, with an estimated 15% to 60% of late acute rejections and 5% to 36% of graft losses associated with nonadherence in solid organ transplant patients (2–5).

Problems with adherence to the prescribed regimen may occur with respect to the taking, dosing, and timing of medication intake; drug holidays may also occur, referring to missing at least two consecutive doses in a row (6). After transplantation, it is not sufficient to take only the prescribed drugs; the timing of medication intake is equally important. Indeed, most immunosuppressive drugs need to be taken twice daily at 12-hr intervals, necessitating medication intake every day at the same time. In contrast to other chronically ill patient populations, even minor deviations from the prescribed regimen (i.e., taking less than 98% of the tablets, taking drug holidays, or variability in timing of medication intake of more than 2 hr) are associated with an increased risk of late acute rejection, graft loss, and poor kidney function (7–10). This evidence shows that immunosuppressant nonadherence should be recognized as an important problem in transplant care.

Several methods aiming to detect nonadherence in transplant patients have been suggested in the literature (e.g., assay, pill count, and prescription refill), but no single method is currently considered as the gold standard. Therefore, Osterberg et al. (11) recommended combining assessment methods or “triangulation” to increase diagnostic accuracy. We believed strongly that the transplant community is in need of tools to identify patients at risk of nonadherence that are accurate and easy to use. It was agreed that self-report was the preferred measurement method in clinical practice, because it is cheap, easy to use (i.e., short), uncomplicated to score, and can easily be combined with other measures often used in clinical practice, such as assay and clinical judgment. This consensus is also supported by evidence showing that self-report is a central component of adherence assessment when a triangulation measurement approach is used (12). Indeed, self-report should never be used in isolation but should be part of a multimethod assessment approach. However, it was unclear which instrument(s) had the best psychometric properties, in view of reliability and validity, which could subsequently be recommended to transplant professionals in the field.

Therefore, the Task Force performed a survey among European transplant professionals, together with a systematic review on the psychometric properties of existing self-report instruments measuring medication adherence, with the aim of proposing validated tools to assess immunosuppressant nonadherence in clinical practice. Validated measurement instruments must be available before adherence-enhancing interventions can be implemented.

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METHODOLOGY

The Task Force members used two strategies to obtain an overview of self-report instruments measuring medication adherence to date. First, all Task Force members contacted the transplant centers and patient organizations within their own country or region, asking for information about the tools used to identify the patients at risk of nonadherence. An enquiry was also sent to the European members of the International Transplant Nurses Society, inviting them to share their instruments with the transplant360 Task Force. No specific inclusion or exclusion criteria were imposed for this part of the project, to provide an overview of as many instruments as possible that are currently applied in clinical practice.

Second, two Task Force members, Fabienne Dobbels and Christiane Kugler, independently performed a systematic literature review of self-report instruments to assess nonadherence in all chronic patient populations. The databases Medline, Cinahl, and Psychinfo were searched, using the following search terms: compliance or noncompliance or noncompliance or adherence or nonadherence or nonadherence or concordance or nonconcordance or persistence or nonpersistence; self-report or scale or questionnaire; validated or psychometric; and medication.

The following inclusion criteria were used: (1) the title and abstract referred to the development or validation of a self-report instrument; (2) the self-report instrument aimed to assess adherence to the medication regimen; and (3) the article was written in English. Only articles published from 1993 to March 1, 2009 were included (i.e., the past 15 years). Articles merely describing a self-report instrument, without describing how the instrument was developed or validated, were excluded, as were instruments developed to assess medication adherence in pediatric patients or psychiatric populations. The search was not limited to transplantation but aimed at identifying all instruments published to date for chronically ill patient populations in general.

Both the instruments identified based on the survey and the published self-report instruments found within the systematic review were evaluated based on the following criteria:

  1. Was a conceptual framework used to develop the instrument, capturing all relevant dimensions of medication behavior, that is, taking and timing of medication intake?
  2. Were the items and their response options able to capture minor deviations from the prescribed regimen?
  3. Was the instrument easy to use and easy to score?
  4. Were the reliability, validity, and responsiveness to change of the instrument thoroughly tested?

These criteria were considered important, because the taking and regularity of medication intake (timing) are both important with respect to the immunosuppressive regimen. Furthermore, even minor deviations from the prescribed regimen are sufficient to result in poor clinical outcomes in heart and kidney transplantation. Finally, transplant professionals require good quality instruments that do not pose an extra burden in terms of workload and time investment (7, 9) and that are reliable, valid, and responsive to change. We used the framework published by Kimberlin et al. (13) to evaluate the quality of the instrument regarding reliability, validity, and responsiveness to change. Table 1 provides an overview of the different types of reliability and validity testing that can be performed to assess the psychometric properties of a given instrument.

TABLE 1

TABLE 1

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RESULTS

Instruments Currently Used at European Transplant Centers

Fourteen instruments were received from Europe (Table 2). However, four instruments referred to interventions, thus they fell beyond the scope of this article as they do not include an adherence assessment instrument (1–4 in Table 2). Three instruments were described in publications on adherence research, but information on their validation process was not published and their items sometimes refer to adherence in general and not to medication adherence specifically (5–7 in Table 2). Two instruments do not address medication adherence specifically but measure barriers or other psychosocial outcomes instead (10 and 11 in Table 2). Two instruments (8 and 9 in Table 2) used in Spain include the same items, which were translated from the Immunosuppressive Therapy Adherence Scale, the only scale with information on its validity published (14). The Immunosuppressive Therapy Adherence Scale will be discussed later in the systematic literature review Results section (12 in Table 2). Finally, two of the instruments currently used in clinical practice specifically measure medication adherence (13 and 14 in Table 2), that is, the Transplant Audit for Transplantation Management and the Basel Assessment of Adherence Scale for Immunosuppressives (BAASIS; indicated in gray in Table 2).

TABLE 2

TABLE 2

TABLE 2

TABLE 2

The Transplant Audit for Transplantation Management is used in Birmingham, United Kingdom, as a screening tool for adherence. However, this instrument was not selected for further consideration as it did not fulfill our aforementioned criteria.

More specifically, the items predominantly focus on the taking of immunosuppressive drugs but do not mention timing or regularity of medication intake. The recall period is rather long (3 months) and is only mentioned on the first item. The scoring seems quite complicated; Visual Analogue Scales are used, on which patients indicate whether they agree or disagree with a given statement, but no specific instructions for interpretation of the scores are available. Furthermore, no information on its validity has been published. We contacted the developers of the scale, who confirmed that the instrument was meant to provide a quick scan of patients at risk of nonadherence, but was not intended for use as a fully validated instrument.

The BAASIS measures both the taking and timing of immunosuppressives. The instrument was developed as an interview, and recall period is limited to the last 4 weeks. The instrument is easy to score, and items have been validated for adherence to antiretrovirals in patients with HIV. More specifically, the item referring to the taking of medication had a moderate to good concurrent validity compared with electronic monitoring and good predictive validity, because it was able to predict virological failure (15, 16). However, its validity in transplant populations needs to be established.

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Systematic Literature Review

Our systematic search of the literature resulted in 317 abstracts, of which 294 were excluded: 17 were not in English, 16 were reviews, 38 dealt with psychiatric populations, 48 were describing measurement scales that did not assess medication adherence, 10 abstracts were concerning pediatric patients, and 168 did not describe a measurement instrument.

Table 3 provides an overview of the 20 identified self-report instruments to assess medication nonadherence, their items, scoring, and interpretation. The conceptual model, reliability, and validity of the instruments are summarized in Table 4.

TABLE 3

TABLE 3

TABLE 3

TABLE 3

TABLE 3

TABLE 3

TABLE 3

TABLE 3

TABLE 3

TABLE 3

TABLE 4

TABLE 4

TABLE 4

TABLE 4

As can be observed in Tables 3 and 4, most instruments refer to only medication taking, making them less suitable for use in transplant populations, given that both the taking and timing of medication intake are important dimensions of immunosuppressive medication-taking behavior. Moreover, not all instruments report the scoring and interpretation of scores, and their psychometric properties in view of reliability, validity, or responsiveness to change have not always been tested.

Based on our predefined criteria (i.e., easy to use and interpret, assessing both taking and timing of medication intake and validated extensively), only two self-report instruments can be recommended for use in transplant populations: the Brief Antiretroviral Adherence Index (AACTG) and the Medication Adherence Self-Report Inventory (MASRI) (indicated in grey in Tables 3 and 4).

The AACTG questionnaire requires assistance from a healthcare professional and is, therefore, more labor intensive. The clinician first makes a list, together with the patient, of all medications taken; the patient is then asked to rate how many doses were missed the previous day, then 2, 3, and 5 days ago, for each specific drug taken. The short recall period makes it easier for patients to remember what has happened during this time. A more general question at the end of the questionnaire asks the patient to indicate the last time a dose of medication was missed. A question is also included asking about regularity of medication intake in general, without referring to a specific time frame. These questions can easily be adapted for use in transplant populations.

The MASRI also starts by asking how many doses were missed yesterday, the day before yesterday, and 3 days ago. However, these answers are not used to determine whether a patient is adherent or not but only serve to stimulate a patient's reflection on his or her medication-taking behavior. The questions that require patients to indicate their percentage adherence, that is, what proportion of doses of the drugs were taken (or taken within 2 hr of the prescribed regimen), might be difficult for patients to comprehend, and answers are largely dependent on the patient's personal reference standard. For instance, a very conscientious patient may report a score of 70 if they were 15-min late with medication intake a couple of times over the last week, whereas another patient who does not know that timing is important may report a score of 90 even if they did not take the tablets at fixed time points. As such, this subjective scoring system may render comparisons between patients difficult.

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DISCUSSION

The goal of this survey and systematic review was to identify self-report instruments that assess adherence to the immunosuppressive regimen and are easy to use and validated.

Before discussing our findings, we need to acknowledge that self-report is not the gold standard for adherence assessment, because some patients may be reluctant to disclose adherence problems or may have problems recalling their medication-taking behavior preceding the assessment. Electronic monitoring is often promoted as the best assessment for adherence research purposes, as it allows monitoring of medication intake and timing over a period of time and has superior validity compared with other measurement methods. However, despite being an accurate and valid tool, its use in clinical practice is limited because (a) most electronic monitoring devices may lead to practical or confidentiality issues as the devices are rather large; (b) their use is labor intensive for professionals; (c) devices are expensive; and (d) they allow monitoring of a single drug only (17).

Taking these points into consideration and given that all existing measurement tools have advantages and disadvantages, the current recommendation is to combine several measurement methods; this is often referred to as “triangulation” (11). Recently, Schäfer-Keller et al. found that the following algorithm showed a sensitivity of 72% and a specificity of 43% when using electronic monitoring as the reference value: self-reported nonadherence or at least one clinician (physician or nurse) reporting nonadherence or subtherapeutic blood levels. More specifically, a patient is considered to be nonadherent if at least one of these measures classifies the patient as nonadherent (12). These methods can be implemented easily in clinical practice but underscore the need for a well-validated self-report instrument as a part of the triangulation strategy.

Given that self-report tends to underestimate nonadherence, selecting the optimal instrument is crucial to allow identification of the maximum number of patients with problematic adherence. Based on our European survey and systematic literature review, consensus was reached within the transplant360 Task Force that three self-report instruments can be recommended for use in transplant clinical practice; the BAASIS, the AACTG questionnaire, and the MASRI, which are available on request from the developers, are recommended for the following reasons:

  • First, all three instruments assess both the taking and regularity of medication intake; both are medication-taking dynamics that are extremely relevant for transplant populations. In contrast to many other drugs, for which timing of intake is less of a concern, immunosuppressive drugs need to be taken at fixed time points and allow only small deviations from the prescribed regimen to maintain good graft function.
  • Second, the instruments seem simple to use and to score, which meets the transplant professional's need for instruments that can be completed easily during busy clinics and also used to guide decisions regarding the necessity of adherence-enhancing interventions. The BAASIS instrument seems to be particularly suitable in this respect, because it only contains four items that can be performed in interview format. All instruments can be completed in about 5 min.
  • Finally, all instruments have been validated and show good psychometric properties. However, validity has only been established in patients with HIV. If these three instruments prove to be valid for transplanted and HIV patients, they can be considered user-friendly self-report adherence assessment tools. A prospective study, using these selected instruments in the transplant population, simultaneously evaluating their reliability and validity relative to electronic monitoring, could serve this purpose. Whether combining self-report instruments increases their diagnostic accuracy also remains to be established. Meanwhile, the instruments can best be used in combination with other measurement methods. Although the recommendations of the Task Force should not be perceived as clinical guidelines on adherence assessment, they will hopefully facilitate assessment of adherence in routine clinical practice and stimulate new research initiatives to determine which combination of adherence measurement methods yield the best diagnostic accuracy.
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APPENDIX

The members of the transplant360 Task Force are as follows: Fabienne Dobbels (Chair), University Hospitals of Leuven and Centre for Health Services and Nursing Research, Katholieke Universiteit Leuven, Belgium; Christiane Kugler, Integrated Research and Treatment Centre, Hannover Medical School, Hannover, Germany; Lut Berben, Institute of Nursing Science of the Faculty of Medicine at the University of Basel, Switzerland; Lisa Burnapp, Guy's and St Thomas' NHS Foundation Trust, London, United Kingdom; Sabina De Geest, Institute of Nursing Science of the Faculty of Medicine at the University of Basel, Switzerland, and Centre for Health Services and Nursing Research, Katholieke Universiteit Leuven, Belgium; Gerda Drent, University Medical Centre Groningen, University of Groningen, Groningen, The Netherlands; Håkan Hedman, Savedalen, Sweden; Annette Lennerling, Transplant Institute at Sahlgrenska University Hospital in Gothenburg, Sweden; Sandra Martin, University Hospitals Leuven, Belgium Catholic School of Nursing, Leuven, Belgium; Dawn McPake, Queen Elizabeth Hospital, Birmingham, UK Birmingham Hospital, Birmingham, United Kingdom; María Sarrias, Hospital Universitari Vall d'Hebron, Spain; Nadine Stohler, Aesch, Basel, Switzerland; Clare Whittaker, Royal London Hospital, London, United Kingdom. The Task Force members were selected based on their expertise on adherence research (Berben, De Geest, Dobbels, Drent, Kugler, and Lennerling), their role as a chair of European patient organizations (Hedman and Stohler), their active membership of the International Transplant Nurses Society (Martin and Whittaker), or their nationally or internationally recognized clinical leadership (Burnapp, McPake, and Sarrias).

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                                                                      Keywords:

                                                                      Transplantation; Immunosuppression; Adherence; Self-report instruments

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