Canada: Validation of a Self-Reported Questionnaire Assessing Adherence to Antiretroviral Medication

The current study aimed to test the validity of a new, brief questionnaire assessing nonadherence to antiretroviral medications. The study recruited 256 participants in four HIV/AIDS clinics, three in Montreal and one in Quebec City. Subjects had to be at least 18, to have known their HIV status for at least six months, and to have been prescribed HAART for at least six months.

At each clinic visit, study nurses asked patients to complete the questionnaire, place it in an envelope and seal it. The questionnaire, plus data from medical records (viral load and CD4 cell count) were used to assess adherence at T0 (baseline), T3 (three-month follow-up) and T6 (six-month follow-up). The investigators used viral load as a criterion to assess the validity of the questionnaire, "because there is growing evidence that virologic failure is associated with nonadherence to antiretroviral medication," the study stated. "Specifically, a patient was considered to be nonadherent only if her/his viral load increased between T0, T3, and T6. Otherwise, the respondent was considered to be adherent, that is, if that patient's viral load decreased, remained similar, or was unstable (an increase followed by a decrease or a decrease followed by an increase) between T0, T3, and T6." The researchers also categorized patients as nonadherent if, for at least one measurement time, they reported having missed taking more than 5 percent of their pills on the day before their clinic visit, the penultimate day before their clinic visit, or during the preceding seven days. They were also classified as nonadherent if they reported not taking their pills during the last 30 days.

Mean age of the participants was 43; most were homosexual/bisexual men with university degrees and jobs. Most had contracted HIV through sexual contact. Most had been living with HIV for more than five years and taking antiretroviral medication for more than three years. Only 5 percent of respondents had injected drugs in the year before the study.

The investigators conducted statistical analyses to identify which questions of the self-reported questionnaire were predictors of nonadherence. Only one question, the number of pills missed during the preceding seven-day period, was found significant. "Therefore, further analyses for sensitivity, specificity, correct classification, and odd ratio were performed for this question," the authors noted. Additional analyses excluding patients with CD4 cell counts of 200 copies per milliliter or less and patients with a CD4 cell count of 200 copies per milliliter or less who also had an unstable viral load between T0, T3, and T6 found the questionnaire had 71 percent sensitivity, 72 percent specificity, 72 percent correct classification and an odd ratio of 6.15.

Of the fact that only the question about the past seven days was adequate to detect nonadherence, the authors suggested that the question was asked after an aided-recall question and after prior questions relating to shorter time periods.

The researchers concluded, "This study has shown that this questionnaire has satisfactory psychometric qualities to assess nonadherence to antiretroviral[s] among patients with HIV. The questionnaire is brief, simple, and can be used in a clinical setting with patients who have been prescribed different antiretroviral regimens. Although the good performance of this questionnaire appears to be related to only one question, that is, the number of antiretroviral pills missed during the preceding 7-day period, it is likely that the effectiveness of this question is related to the structure of the questionnaire, helping respondents reduce memory errors and report the number of antiretroviral pills missed during the preceding seven days more accurately."

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