AIDSImpact.com:: - Santa Fe, USA 2011

Abstract #55 - Using the Theory of Planned Behaviour to understand intentions to adhere to antiretroviral therapy in a South African sample.
Authors: Presenting Author: Dr. Ashraf Kagee - Stellenbosch University
Additional Authors: Ms. Wylene Saal,
Aim: The objective of the study was to determine the extent to which the Theory of Planned Behaviour (TPB) was applicable in predicting adherence to antiretroviral therapy (ART) among South African persons living with HIV. Considerable evidence has shown that sub-optimal adherence can lead to lower CD4 count, higher viral load, mortality, poor quality of life, and an increase in patients’ risk of developing resistant strains of HIV. Ensuring optimal adherence is essential in decreasing patient mortality, improving quality of life, and limiting wastage of drugs, clinicians’ time, and clinic resources.
Method / Issue: One hundred and seven patients receiving antiretroviral treatment were recruited by means of convenience sampling at a peri-urban public hospital in South Africa. Patients were asked to complete a battery of questionnaires that included the Adherence Attitude Inventory (AAI), a 28 item instrument; an eight-item questionnaire developed to assess perceived subjective norms; an eight-item scale developed to assess perceived behavioural control; an eight item three response option constructed to measure intentions to engage in various adherence-related activities; the HIV stigma scale, a 40 item instrument with four subscales; and a self-reported adherence scale that inquired about the number of dosages missed over a seven day recall period. Regression analysis was used to determine the proportion of variance explained in adherence behaviour by the linear combination of the TBP variables and perceived stigma.
Results / Comments: The linear combination of the TPB variables explained 12% (R2 = 0.12) of the variance in intentions to adhere to treatment, F (3, 97) = 4.52, p = 0.01. This represents a small to medium effect size. In the second step perceived stigma was added to the variables in the first step and explained 3% of the variance in intentions to adhere to adherence. However, the difference in R2 was non-significant, F (1, 96) = 3.09, p = 0.08. Perceived behavioural control significantly predicted adherence intentions while attitudes towards treatment and perceived subjective norms were non-significant predictors. Thus patients who feel confident that they can adhere to their prescribed regimen may be more likely to have strong intentions to adhere to treatment. This finding is consistent with other research showing that perceived behavioural control is strongly related to intentions to adhere to treatment. Perceived stigma was negatively but non-significantly related to intentions to adhere. We found a non-significant relationship between intentions to adhere and self-reported adherence.
Discussion: The TPB was shown to account for a small but significant proportion of the variance in intentions to adhere to ART, but not to actual adherence behaviour. Possible reasons for the lack of association between these two variables include the possibility that the instrument used to measure adherence may have been vulnerable to recall bias and social desirability bias. The study suggest that the TPB may have utility in predicting adherence intentions among South African patients but that further research is needed to assess self-reported adherence.
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