Abstract
Background/Aims A refined understanding of risk factors for unfavorable virologic responses among HIV-infected patients who recently switched antiretroviral regimens is needed. We investigated the effects of HIV disease factors, antiretroviral use history and patient-level factors on virologic outcomes after an antiretroviral regimen switch.
Methods We identified HIV-infected patients who changed antiretroviral regimens between 2001–2008 at Kaiser Permanente Southern and Northern California. Baseline was the date of a switch to a new antiretroviral therapy regimen, defined as adding =2 new medications. HIV virological response, measured after 6 months on the new regimen, was classified as:
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achieving maximal viral suppression (HIV RNA<75 copies/mL),
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low level viremia (LLV; HIV RNA between 75–5000/mL), or
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advanced virologic failure (>5000 copies/mL).
Potential risk factors examined included:
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HIV disease factors, e.g., prior AIDS, CD4 cell count;
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history of antiretroviral use, e.g., duration of use, number of regimen prior to switch, therapy classes of the new regimen [e.g., protease inhibitor (PI)-based, nucleotide reverse transcriptase inhibitor (NRTI)-based], medication adherence, and virologic failure of previous regimens and
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patient-level factors including demographics, comorbidities and healthcare utilization. Adjusted odds ratios (aOR) for unfavorable virological outcomes, i.e., LLV and advanced virologic failure, were obtained from multivariable nominal logistic regression models with terms for potential risk factors associated with these outcomes (P<0.10) in the crude analysis.
Results There were 3447 patients who underwent antiretroviral regimen switch during 2001–2008. At 6 months after baseline, 2608 (76%) achieved maximal viral suppression, 420 (12%) had LLV and 419 (12%) developed advanced virologic failure. Factors associated with increased odds of LLV and advanced virologic failure included: number of regimen prior to switch [aOR=1.37 (1.17–1.62) and 1.8 (1.5–2.1), respectively], NRTI-based regimen (vs. PI-based) [aOR=2.77 (1.27–6.02) and 5.1 (2.4–10.9), respectively] and virologic failure at previous regimens [aOR=3.16 (2.18–4.58) and 4.7 (2.8–7.8), respectively]. On the other hand, older age, higher CD4 cell count, and higher medication adherence were associated with reduced odds of unfavorable virologic outcomes.
Discussion History of virologic failure, immunodeficiency and antiretroviral regimen-level factors were significantly associated with virologic failure after a recent therapy switch and should be considered when making treatment change decisions.
