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CARDIOVASCULAR JOURNAL OF AFRICA • Volume 30, No 2, March/April 2019
AFRICA
115
and German (0.73). Relevant studies demonstrated that the
Hill–Bone questionnaire is a valid and reliable instrument for
measuring adherence to hypertension treatment, which allows
for the assessment of self-reported compliance in patients and
therefore for planning adequate treatment.
14-16
The Treatment Adherence Questionnaire for Patients with
Hypertension (TAQPH) is a scale developed in 2011, comprising
28 items evaluating six adherence domains: pharmaceutical
treatment (nine items), diet (nine items), exercise (two items),
stimulation (three items), weight control (two items) and coping
with stress (three items). Answers are provided using a four-item
Likert scale and the total score is between 28 and 112. Higher
scores indicate better adherence. The Cronbach’s
α
for the entire
questionnaire was 0.86 and 0.82, indicating good psychometric
properties.
17
The questionnaire has been translated into Farsi,
and subsequent validation demonstrated its good psychometric
properties (
α
=
0.80) and strong correlation with the Morisky
scale (
p
=
0.27).
The Brief Medication Questionnaire (BMQ) is likely to be the
oldest available questionnaire measuring adherence to treatment
and barriers to adherence. Its authors intended to develop a
simple but sensitive and accurate instrument for identifying
causes of non-adherence, also in patients treated with multiple
medications. The questionnaire comprises five items related to
medication-taking in the two preceding weeks, the perceived
effectiveness of the treatment, any inconvenience it causes, and
possible difficulties related to the treatment and its dosage. It is
composed of three different screens. The first one, a five-item
regime screen, assesses medication-taking in the preceding week;
the two-item belief screen assesses the effectiveness of the drug
and any inconveniences experienced by the patient, and, finally,
the two-item recall screen assesses problems the patients faced
with regard to remembering their medication.
18
The Compliance of Hypertensive Patients Scale (CHPS)
was developed by Lahdenperä
et al
.
19
to provide information
regarding patients’ intentions, responsibility and co-operation
with regard to treatment adherence. The items are grouped
into five subscales: lifestyle, intention, attitude, responsibility
and smoking. Inter-item correlations and corrected item total
correlations across subscales are 0.24–0.61 and 0.32–0.67,
respectively. With regard to the theta coefficient, good internal
consistency was observed. The scale has not been used by other
authors.
19
The Facilitators of and Barriers toAdherence toHypertension
Treatment Scale (FATS) is an 18‑item scale evaluating beliefs
related to treatment and causes of adherence and non-adherence
to treatment. The authors’ aim was to develop a culturally
sensitive measure of barriers to hypertension treatment
adherence in African and black American women. Qualitative
studies performed in hypertensive patients suggest three
categories of factors associated with adherence to hypertension
treatment: beliefs about hypertension, facilitators of adherence,
and barriers to adherence. The questionnaire comprises four
subscales: social support, knowledge on hypertension, self-care
and adherence-enhancing behaviours, and barriers to adherence.
The
α
coefficient for the 18-item FATS was 0.78.
Regarding the multivariate regression model, which was
the control for the blood pressure stage, it revealed that the
FATS significantly correlated with the Hill–Bone High Blood
Pressure Compliance Scale (standardised
β
=
0.35;
p
=
0.0014).
The questionnaire was only used by the authors of the original
version.
20
The Self-efficacy for Appropriate Medication Use Scale
(SEAMS) was developed for use in low‑literacy patients. Its
psychometric properties were tested on 436 patients hospitalised
for ischaemic heart disease and other cardiovascular diseases,
including hypertension. Its reliability was evaluated by measuring
internal consistency and test–retest reliability. Reliability and
validity analyses were also performed separately among patients
with low and higher literacy levels. The initial 21-item scale was
ultimately reduced to 13 items. Internal consistency reliability of
the instrument is good: alpha reliability is 0.89 in low-literacy
populations and 0.88 in populations displaying high literacy.
(Responses are scaled with the use of a three‑item Likert scale,
with 1, not confident; 2, somewhat confident; and 3, very
confident. It was found that 52.3% of the variance was explained
by a two-factor solution.
The scale’s effectiveness proved to be similar with different
levels of literacy, which suggests that the instrument can be
used with patients whose literacy skills are not at a high level.
21
With its high level of reliability and validity, the SEAMS is an
appropriate tool to assess self-efficacy for medication use in
patients suffering from chronic diseases.
Adherence measures applicable to AF
The available publications on AF mainly focus on adjustment
to anticoagulant therapy. A review of reports that have been
published on the evaluation of adherence to treatment in AF
showed the Morisky Medication Adherence Scale, described
above, to be the most commonly used adherence questionnaire in
this area as well. Studies by Patel
et al
.
22
and Jankowska-Pola
ń
ska
et al
.
23
used the eight-item version for measuring adherence to
anticoagulant treatment, while the study by Castellucci
et al
.
24
used the four-item version.
Published reports on adherence to treatment for AF
most commonly use other adherence measures.
25
These are
the population’s medication possession ratio (MPR) and the
proportion of days covered (PDC).
26-28
In this context, adherence
was defined as an MPR or PDC
≥
0.8. In most cases MPR
and PDC are expressed as percentages of the time to which the
medication pertains. MPR is the sum of the days’ supply for all
fills of a given drug in a particular time period, divided by the
number of days in the time period:
MPR
=
Sum of days’ supply for all fills in period
________________________________
Number of days in period
×
100%
Compared to MPR, PDC is a more conservative estimate of
adherence. The two have a similar formula, but PDC focuses on
‘coverage’ rather than days of supply:
PDC
=
Number of days in period ‘covered’
____________________________
Number of days in period
×
100%
Studies on adherence to anticoagulant treatment in atrial
fibrillation commonly use scales of satisfaction with anticoagulant
treatment. The Anti-Clot Treatment Scale (ACTS) is one of the
most commonly used patient-reported scales. It is a 15-item scale,
comprising a 12-item burdens scale and a three-item benefits
scale. The ACTS burdens items use a five-point Likert scale,
where 1 is the rating for ‘extremely’ and 5 is for ‘not at all’.