Poor adherence to anti-HIV treatments is associated with a lack of knowledge of HAART dosing requirements and low levels of literacy, according to a US study published in the 15th February edition of the journal Clinical Infectious Diseases, which is now available on-line.
Investigators recruited 126 patients involved in the Adherence and Efficacy Protease Therapy (ADEPT) study to a prospective, observational trial to see if there was a link between patient knowledge of medication dosing and levels of adherence.
Patients were intensively evaluated for adherence at four-weekly intervals, with at least two visits during a 48 week period necessary for inclusion in the study. Clinical data were collected from medical records. In addition, at four-weekly intervals interviews were conducted by clinical trial nurses including questions on literacy, symptoms of depression, social support, satisfaction with medical care, trust in their healthcare, and belief in the value of their anti-HIV therapy, to see what factors could be associated with adherence.
At enrollment to the study and again at weeks eight, 24 and 48, patients were asked to name the medicines included in their anti-HIV treatment regimen; says how many times a day each medicine had to be taken; and to say how many pills had to be taken in each dose. Nurses noted whether patients were using an aid to help them to remember to take their medication. A score of medication knowledge score (MKS) was calculated from the patients’ answers.
Patient adherence was measured using three methods: four-weekly pill counts; patient reporting; and by the use of Medication Event Monitoring System (MEMS) bottle caps which record each time a pill bottle is opened.
Analysis of baseline results showed that almost a quarter of patients prescribed a new HAART regimen lacked essential knowledge about their medication. Only 80% could correctly identify the drugs they were prescribed; 72% the number of times a day their pills needed to be taken; and 74% the number of pills which each dose consisted of.
Knowledge improved to an average 90% by week eight and remained at this level throughout the rest of the study. Knowledge at week eight was found by the investigators to be strongly predictive of adherence in both the preceding and subsequent weeks of the study. Average adherence throughout the study was suboptimal at 71%, however knowledge of the anti-HIV medicines prescribed and their dosing requirements improved adherence, with each 0.10 increase in MKS associated with an increase in adherence of approximately 2%.
As knowledge of medication at week eight was found to be such a strong predictor of both earlier and later adherence, investigators tried to establish which factors were associated with patient medication knowledge at this time. Poverty (income below $10,000 a year); failure to complete secondary education (high school); low levels of literacy; and never participating in a clinical trial were all found to have such an association. When the results were subjected to a multivariate analysis, low literacy levels were found to be an independent factor of poor medication knowledge and adherence.
The investigators further observe that patient attitudes and beliefs, “factors usually strongly associated with medication adherence were not associated with dosing knowledge.” Nor were clinical factors or being prescribed more complex HAART regimens.
On the basis of their finding the investigators suggest that patients who have recently started HAART or changed their treatment regimen should be questioned soon after to assess adherence. They conclude that patients with low levels of literacy should be asked to verbally describe their understanding of their medication’s dosing requirements and that “specific interventions should target patients with low levels of education and literacy to help them learn dosing instructions.”
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Miller LG et al. Knowledge of antiretroviral regimen dosing and adherence: a longitudinal study. Clinical Infectious Diseases 36 (online edition), 2003.