Discussion
To our knowledge, this is the first study examining the level of usual
care by HCPs to support adherence to statins and the impact of the level
of usual care on patients’ adherence to statins. The results of this
study did not confirm the hypothesis that there is a positive
relationship between the extent of HCPs’ adherence supporting activities
in usual care and patients’ implementation adherence to statins. The
extent of usual care activities hardly differed between physicians,
pharmacists and pharmacy technicians. The median sum scores on all sub
scales of the Quality of Standard Care questionnaire were comparable for
all HCPs, only on awareness physicians scored higher than pharmacy
staff.
In this study the level of usual care to support adherence delivered by
physicians is comparable and by pharmacists exceeded that reported by
Timmers et al (in patients using oral anti-cancer drugs).36. The latter might be explained by the fact that
other HCPs than pharmacists (e.g. nurses) perform these activities
(because of differences in setting and type of medication).
In our study, both pharmacists and physicians reported that half of the
adherence supporting activities were performed and half were not. When
HCPs coordinate their adherence supporting activities, this does not
necessarily have to be a problem. This seems to be the case with respect
to patient education to improve medication adherence: whereas doctors
educate patients about the disease, the effect of the drug and treatment
duration, pharmacy staff member tend to focus on adverse events,
drug-drug interactions and storage conditions. Although doctors and
pharmacy staff members seem to be synergistic with respect to education
(sending information), neither doctors nor pharmacy staff members ask
the patient about perceived barriers to take the medication as
prescribed: patients’ knowledge about medication and non-practical
barriers and practical barriers taking medication as prescribed are
hardly inventoried by both physicians and pharmacy staff.
The extent of usual care of HCPs to support adherence to statins was not
positively associated with patients’ adherence to statins. This in
contrast with two meta-analyses on the quality of usual adherence care
and medication adherence in patients infected with Human
Immunodeficiency Virus (HIV) showing that a higher quality of
self-reported usual care led to more patients being adherent to their
medication 28,29. This might be explained by
differences in type of medication, and design and setting
(cross-sectional inventory of usual care in our study in one country
versus retrospective inventory of usual care in usual care arms of
trials in several countries). Furthermore, in HIV care often nurses are
involved, which requires another role of pharmacists with respect to
adherence support. Finally, adherence was measured differently, as in
our study the MARS questionnaire was used and in the studies included in
the meta-analyses by de Bruijn et al. (2009 and 2010) both self-reported
adherence measures and MEMS devices were used.
The lack of positive impact of usual care of both physicians and
pharmacists to support adherence to statins on patients’ adherence to
statins may be explained by conceptual differences (the extent of
unintentional and intentional non-adherence aspects that are
incorporated in the questionnaire) between the usual care activity
questionnaire and the patient adherence measure (MARS-5). The Quality of
Standard Care questionnaire is balanced with respect to the proportion
of aspects related to unintentional and intentional non-adherence,
whereas the MARS-5 questionnaire used in this study is predominantly
focused on intentional non-adherence. Another explanation may be that
the overall high MARS-scores might lead to ceiling effects, which may
account for not finding a difference in adherence scores, as described
in the strengths and limitations section.
Furthermore, HCPs with a patient population with low adherence rates to
statins possibly feel a greater need to perform activities to support
adherence to statins and consequently have higher scores on the usual
care questionnaire. Alternatively, social desirability bias may have led
to an overestimation of the level of usual care reported by pharmacy
staff. In that case HCPs provide less activities to support adherence
than they say they deliver, tentatively resulting in lower adherence
rates and no (or weakly negative) association between the extent of
adherence supporting activities and patients’ adherence. Participatory
observations to assess the actually delivered extent of usual care
activities to support adherence could be applied to overcome this.
The current findings should be interpreted in light of the strengths and
limitations of our study. One of the strengths of this study concerns
the large sample of patients and HCPs, as well as the high response
rate, which increases the accuracy of the results. This study was
furthermore carried out in a large number of practices across the
Netherlands. This last aspect increases the generalizability (with
respect to adherence supporting activities of HCPs to stimulate
patients’ adherence to statins). The fact that the MARS-5 scores of
patients using statins in this study were similar to those in another
study and that 18% of patients are non-adherent to therapy (similar to
the degree of non-adherence in other studies among Dutch patients taking
statins), is a prove that a valid sample was included in the study and
highlights generalizability 37-39.
However, this study does have its limitations. First of all, self-report
questionnaires were the only means used in this study to measure
adherence and the level of usual care. Questionnaires of this kind are
subjective and therefore sensitive to social desirability bias. It is
preferable for that reason to use a combination of methods when
measuring adherence (e.g. self-report questionnaires, pill count, refill
adherence, medication event monitoring systems and/or biochemical
testing) and to observe the HCPs to inventory the level of usual care.
If the extent of usual care delivered by a HCP is assessed by
observation, it can be decided to observe each HCP once, or to observe
all individual patient-provider interactions. Preferably all the
individual patient-provider interactions are observed, as the usual care
actually provided may depend on a specific patient and/or moment. Seeing
that it is likely that adherent patients are more motivated to
participate in a study of this kind (confirmed by slightly higher
adherence rates in this study than in other studies), inclusion bias may
have played a role 3,8. The chance that inclusion bias
has affected the results, however, is reduced by that fact that the
response rate of patients was high (67.5% of the selected patients
agreed to participate in the study). Furthermore, due to a ceiling
effect when using the MARS-5 and therefore little explained variance, no
difference in adherence scores may be found.
This study provides an overview of usual care activities to support
adherence to statins as reported by a large number of physicians,
pharmacists and pharmacy technicians employed in a large number of
practices in the Netherlands. Furthermore, the results of this study
suggest that there is no positive relationship between the extent of
HCPs’ adherence supporting activities in usual care and patients’
adherence to statins. Before trials are performed to improve adherence
by intervening on HCPs, first more research with better techniques to
objectify the level of usual care to support adherence and the impact on
patients’ adherence is warranted. As only questionnaires were used in
this study to examine the impact of usual care on adherence, further
research in which other methods to measure adherence are used are
recommended. Further research could furthermore be supplemented with
observing the patient-provider interactions to inventory the level of
usual care delivered by HCPs.