Adherence to Inhaled Corticosteroids and Patient Perception : Towards a better understanding and individualised care

Abstract

In this thesis we aimed to further deepen knowledge on factors associated with nonadherence to provide means to improve adherence. We evaluated several methods of assessing adherence. At first, we evaluated the accuracy of the Medication Adherence Rating Scale (MARS), a structured method for eliciting patients’ reports of adherence, in identifying low adherence with ICS using prescription refill data as a reference. We found that the MARS as a self-reported measure of adherence is useful as a screening tool for identifying patients with low adherence to ICS. Furthermore, we investigated the use of ICS during a ten-year period to describe medication use as a continuum. With this approach we could expand research further than identifying those patients who persist and also investigate recurring episodes of non-persistence. We found that patients most frequently discontinued in the year after start. In conditions like asthma, self-management allows patients, depending on their severity of disease, to adjust the timing and dosing of inhaled corticosteroids (ICS). Why patients behave in a particular way or make certain decisions is not easy to deduce from the pharmacy records available in most studies on adherence. In Chapters 3 and 4 we evaluated possible driving forces behind certain adherence behaviour. Discontinuation of ICS treatment has been widely discussed and some investigators had found similar results as ours, in new users of other medication. However, few studies investigated diagnoses assigned to new users of medication by the physician and it’s influence on adherence. Furthermore to the best of our knowledge, patient and physician reasons for discontinuing have not been investigated in depth. Therefore we aimed to describe reasons for prescribing and discontinuing ICS from a patient perspective (Chapter 3.1) with clinical information, obtained from the GP, added (Chapter 3.2). To our surprise patients primarily mentioned a variety of self-limiting symptoms like cough and dyspnoea or conditions like common cold, acute bronchitis and pneumonia for which ICS are not indicated. General practitioners stated to be certain on a diagnosis of asthma in almost one quarter of their patients. Moreover, in almost 30% of their patients they had a suspicion of asthma. The discrepancy between the opinions of GPs and patients indicates that the communication of the reason for prescribing drugs like ICS should be improved. As knowledge of treatment and actions of a drug have been shown to influence adherence and self-management we investigated in chapter 3.3 the knowledge of ICS’ mode of actions among new users of ICS that discontinued, and whether they were instructed on the use of their inhaler. The majority of patients were not aware of ICS’ actions. The way in which patients are instructed on their inhalers should be improved, especially giving attention to knowledge on the anti-inflammatory effects of ICS. Previously the beliefs about medicines questionnaire (BMQ) was shown to correlate with self-reported adherence. In chapter 4.1 we investigated whether beliefs about ICS, measured by the BMQ (necessity and concerns), relate to adherence objectively measured by prescription refill records. Based on the relations found we conclude that the BMQ specific and general could be used to identify specific barriers on the use of medication of individual patients. For this purpose we defined four attitudinal groups, based on the BMQ necessity and concerns constructs, in an attempt to translate particular beliefs to certain types of patients and facilitate medical decision making by recognising patients who will most likely be non-adherent. The attitudinal groups differ in perceived harmfulness towards medicines in general and in adherence by self-report and pharmacy data. In chapter 4.2 we evaluated whether the level of disease control influenced the relation between the BMQ and adherence since it has been hypothesized, e.g. within Leventhal’s common-sense model, that symptom experience might influence adherence or mediate the relation between adherence and perception. We found that in patients with less adequate disease control more attention for beliefs and symptom control is needed, as the correlations between perceived need of ICS and adherence are weakest in patients with lowest disease control. Symptom control can be evaluated (in the pharmacy) by use of the Asthma Control Questionnaire (ACQ) and use of short-acting beta2-agonists (SABA). In this way it can be verified whether certain experienced symptoms are followed by the correct self-management actions or accompanied with a particular perception, e.g. whether a relatively high reported need for ICS is accompanied with a preference to use a SABA or even an ICS as needed when experiencing dyspnoea, rather than using the ICS for prevention. Based on our findings the effectiveness of interventions can be improved by tailoring to an individual patient’s needs. For this purpose we provide clinical implications of the findings in each chapter, including the general discussion.