Effective use of antiretrovirals requires a high level of adherence on the part of the patient. Levels of adherence to HAART below 95% are associated with poor virological and immunological response, and with more days in hospital. Maintaining this degree of adherence presents significant challenges. Current advice is that HAART should be prescribed for chronic use, and to patients whose HIV infection is asymptomatic. Treatment may result in significant toxicity, and may involve the use of complex regimens which may impact negatively on quality of life. Experience from clinical settings finds that many people taking HAART achieve levels of adherence below 95%.
The general literature suggests that poor adherence is multi-faceted and unpredictable, and research in the HIV field supports this. Factor analyses which have attempted to identify characteristics that are predictive of poor adherence have largely failed to produce consistent findings, aside from an association with psychological and psychiatric problems. Patients themselves report forgetfulness and drug toxicity as the most common causes of missed doses.
Dietary restrictions may also impact negatively on adherence, and regimens which are dosed once or twice a day may facilitate better adherence than those dosed more frequently, though this may still fall short of the level required for a successful response.
In addition to these practical issues, patients' perceptions of their therapy are influential. Good adherence has been associated with higher levels of self-efficacy, i.e. belief in one's capacity to follow the regimen. Similarly, adherence may also be related to the individual's beliefs about treatment, particularly to doubts about the necessity for good adherence and to concerns about potential adverse events. People who understand the relationship between adherence and drug resistance should also be expected to report higher levels of adherence.
Adherence to antiretroviral therapy will be most likely where patients are committed to their therapy, and have been fully involved in selecting an appropriate regimen. However, adherence is a process and not a single event. Interventions to support adherence should be multi-faceted, responsive to the needs of the individual, and an integral part of ongoing care which is offered to all patients. Such programmes require investment and dedicated, trained personnel, but are essential to realising the benefits of expenditure on HAART.
In an asymptomatic individual the decision to begin therapy is complex and should not be made in haste. Counselling, education and peer support are required prior to starting therapy, and whenever a regimen is changed. The summary table below describes the minimum of a range of patient and medication variables which should be considered by clinicians and their supporting health care professionals at each patient visit.
Promoting adherence: Issues to consider
The motivation of the individual to begin and continue therapy
The individual's understanding of the importance of adherence and its relationship to drug resistance
The impact of therapy on the individual's lifestyle and psychological well-being
The provision of memory aids to establish and maintain a pill-taking routine
Treatment of any underlying mental health problems
Management of side-effects
The potential risks and benefits of therapy, both real and perceived, in the short and long-term
The provision of written information to provide support outside the clinic setting
BHIVA have established a working group whose task is to consider the evidence to support more detailed guidelines on the establishment of core adherence support services within clinical and community settings. A consensus document will be available in due course.