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July 19, 2011

IAS 2011: Interpreting the Data: Selection Bias?


Interpreting the Data: Selection Bias?

In a poster presentation, investigators from Abbott Laboratories (United States) discussed Cardiovascular disease (CVD) risk in human immunodeficiency virus-1 (HIV) infected subjects preceding exposure to antiretroviral therapy.

The temptation is to disregard this study because it appears to be industry-sponsored. However, bear with me for a minute, because their hypothesis is sound: “Some observational studies of HIV-infected patients have identified an association between antiretroviral (ARV) class and CVD events, while others found no association. Observational study subjects are not randomized, therefore it is possible uncontrolled baseline CVD-related factors contribute to discrepancies among studies. This study objective was to determine if there are baseline differences in CVD risk, CVD-related morbidity and HIV-related morbidity between subjects initiating ARV treatment containing a protease inhibitor (PI) vs. non-nucleoside reverse transcriptase inhibitor (NNRTI).”

Based on their data, it would appear that selection bias may play a role in results from observational cohorts. In 3973 subjects (mean age 42.7 years), the PI cohort (n=1280) vs. NNRTI cohort (n=2693) had significantly greater prevalence of chronic ischemic heart disease, diabetes, cardiomyopathy, heart failure, dysrrythmias, and non-hypertensive kidney dysfunction.

They conclude that: patients prescribed PIs had increased baseline prevalence of CVD risk factors, CVD-related morbidity and HIV-related morbidity when compared with subjects receiving NNRTIs. These results may help future observational analyses better control for potential confounders when investigating ARV-associated CVD risk.

Reporter Comment: points well-taken. The authors don’t say it, but it would be helpful to answer these questions with a prospective stidy. Absent that, the old rules still apply in terms of individualizing therapy. In view of newer, potent agents and new classes of drugs, optimizing therapy while minimizing risk to patients is the order of the day for HIV clinicians. With all of these options available, it makes sense to consider PI and abacavir-sparing regimens in people with cardiovascular risk factors.

Reference: Zachry W, Griffith J, Wegzyn C, Woodward C, et al. Cardiovascular disease (CVD) risk in human immunodeficiency virus-1 (HIV) infected subjects preceding exposure to antiretroviral therapy [Abstract]. July 19, 2011 at the 6th IAS Conference on Pathogenesis, Treatment and Prevention, Rome, Italy. Abstract TUPE242.


Source: Reporting for PRN News from Rome, Italy: Bill Valenti, MD