Tenofovir/emtricitabine (TDF/FTC) plus efavirenz was by far the most popular first-line antiretroviral therapy (ART) among Swiss HIV Cohort Study (SHCS) members starting treatment from January 2005 through December 2009. An AIDS diagnosis and a higher viral load favored prescription of the second most popular regimen, TDF/FTC plus lopinavir/ritonavir.

The analysis involved 1957 antiretroviral-naive adults starting their first regimen. Nearly 30% began treatment with TDF/FTC plus efavirenz, while about 17% started TDF/FTC plus lopinavir/ritonavir and lower proportions started other combinations:

• TDF/FTC plus efavirenz: 29.9% • TDF/FTC plus lopinavir/ritonavir: 16.9% • TDF/FTC plus atazanavir/ritonavir: 12.9% • Zidovudine/lamivudine (ZDV/3TC) plus lopinavir/ritonavir: 12.8% • Abacavir/lamivudine (ABC/3TC) plus efavirenz: 5.7%

First regimen choice differed significantly between SHCS sites (P < 0.001).

Multivariate analysis identified the following factors favoring prescription of TDF/FTC plus lopinavir/ritonavir over TDF/FTC plus efavirenz, at the following relative risk ratios (RRR) (and 95% confidence intervals):

• Prior AIDS: RRR 2.78 (1.78 to 4.35) • Viral load above 100,000 copies/mL: RRR 1.53 (1.07 to 2.18) • CD4 count above 350 cells/μL: RRR 1.67 (1.04 to 2.70)

Three factors favored prescription of TDF/FTC plus atazanavir/ritonavir over TDF/FTC plus efavirenz:

• Depressive disorder: RRR 1.77 (1.04 to 3.01) • Viral load above 100,000 copies/mL: RRR 1.54 (1.05 to 2.25) • Being in an opiate substitution program: RRR 2.76 (1.09 to 7.00)

Two factors favored prescription of ZDV/3TC plus lopinavir/ritonavir over TDF/FTC plus efavirenz:

• Female sex: RRR 3.89 (2.39 to 6.31) • CD4 count above 350 cells/μL: RRR 4.50 (2.58 to 7.86)

After the first 12 months of therapy, 1715 cohort members (87.6%) had a viral load below 50 copies/mL. During that time, CD4 count rose by a median 137 cells/μL (interquartile range 89 to 269). Virologic suppression was more likely among people starting TDF/FTC plus efavirenz than other regimens, but CD4 counts rose more with ZDV/3TC plus lopinavir/ritonavir.

The noted trend toward individualized ART prescribing suggests to the investigators that physician preference and patient characteristics significantly influence choice of a first regimen. They believe their study “highlights the need for evidence-based data for determining the best initial regimen for different HIV-infected persons.”

By Mark Mascolini

Source: Luigia Elzi, Stefan Erb, Hansjakob Furrer, Bruno Ledergerber, Matthias Cavassini, Bernard Hirschel, Pietro Vernazza, Enos Bernasconi, Rainer Weber, Manuel Battegay, for the Swiss HIV Cohort Study. Choice of initial combination antiretroviral therapy in individuals with HIV infection: determinants and outcomes. Archives of Internal Medicine. 2012; 172: 1313-1321.

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