What this paper adds
- Providing a measure combining the evaluation of self-care and
proportion of doses, constitutes innovation that contributes to an
accurate assessment of medication adherence.
- The Global Assessment of Medication Adherence Instrument (GEMA)
presented good practicality, acceptability, and evidence of
specificity regarding the stability of the INR.
- The GEMA proposes the rescue of the memory about the use of the
medicines prior to their evaluation of the adherence in order to
improve the accuracy of the measurement.
- The evaluation of sensitivity and specificity of the measure
contributes of the refinement of the measure of adherence, besides
guiding the choice of measurement.
INTRODUCTION
In the treatment of chronic no communicable diseases (NCDs), adherence
to medication use has been associated with optimization of clinical
outcomes, especially better disease control,1,2reduction of hospitalizations,1mortality,3 and health care costs.4However, the percentage of medication nonadherence remains high.
Medication adherence is one of the most complex self-care behaviors in
the treatment of NCDs.5 According to the middle-rangeTheory of Self-care of Chronic Illness , self-care can be defined
as a process of health maintenance by means of health practices and
disease management, which can be applied to health and disease
situations.6 In this context, the maintenance of
self-care refers to behaviors to maintain well-being, health and
physical and mental stability, such as smoking cessation, healthy food
consumption, stress management, and medication adherence.
Nurses have a central role in promoting self-care,7especially regarding medication adherence, which implies an assessment
and a decision on the need to intervene. However, the measure of this
behavior has shown to be extremely complex.
There are several difficulties in measuring
adherence.8,9 Although there is no consensus on a
”gold standard”,10 self-report instruments have been
indicated as the best option for measurement of adherence, with regard
to ease of implementation, low cost, flexibility (time and mode of
administration), and low burden on the respondent. However, self-report
instruments present potential disadvantages, especially social
desirability and memory bias, which compromise the accuracy of this type
of measure.11
Several self-report scales that measure adherence in chronic diseases
are available in the literature.12-14 TheMorisky Medication Adherence Scale (MMAS) consisting of four
items (MMAS-4) or of eight items (MMAS-8) are the ones of the most
frequently used tools.15,16 However, reports of
overestimation of adherence with the use of self-reported measures have
been frequent.
In order to provide an accurate measure of medication adherence, theGlobal Evaluation of Medication Adherence Instrument(GEMA)17 was developed based on the previous
study.11 The GEMA assumes that adherence is a complex
and dynamic behavior, defined as ”taking medication for treatment,
exactly as prescribed, which means, taking it every day, at the time and
amount indicated, remembering the care needed when taking it, ”before
and after meals and/or at bedtime”.17 This instrument
proposes, in addition to the measurement of the proportion of doses, the
assessment of self-care associated with medication intake. In addition,
to reduce memory bias, GEMA proposes to access the memory to retrieve
the proportion of doses taken in different periods, up to the period of
interest for measurement: that is, the month prior to the interview.
This new instrument seeks to fill the gaps in the literature regarding
the imperfections of self-report measures.18 Although
the GEMA has been used in previous studies,17,19-21 to
our knowledge, no study investigated its properties of the measurements.
The objective of this study was to evaluate the measurement properties
of the GEMA when administered to patients taking oral anticoagulants
(OAC) in an outpatient follow-up. The feasibility, acceptability,
sensitivity, specificity, positive predictive value (PPV), negative
predictive value (NPV) were investigated; the validity of the convergent
construct was tested with self-reported adherence measures and
International Normalized Ratio (INR) stability.
METHODS
2.1 Design and setting
This was a methodological study conducted in an OAC outpatient clinic of
a large university hospital, in the interior of the São Paulo state,
Brazil.
2.2 Sample
The study included 127 adult patients taking OAC in an outpatient
follow-up service. Patients who had been using OAC for at least six
months were included. Patients whose OAC dosage was modified in the last
month prior to the interview, who presented hemorrhagic or
thromboembolic complications in the last three months, or who underwent
surgery in the last six months prior to the interview were excluded.
2.3 Sampling process and sample size
The sample consisted of all the patients who met the inclusion criteria,
from January to March of 2016. In the outpatient clinic, 200 patients
were treated with OAC; of these, 177 agreed to participate; 50 were
included in the pilot sample, and excluded from the final sample. Thus,
the final sample consisted of 127 patients.
2.4 Data Collection Procedure
Data were obtained by means of interview, using instruments. The results
of the last three INR dosages, and the individual therapeutic goal
recommended for each patient, were obtained from the medical record.
2.5 Instruments
2.5.1 Instrument of Sociodemographic and Clinical Characteristics: was
developed in a previous study22 and was submitted to
content validity.