Is zidovudine first-line therapy virologically comparable to tenofovir in resource-limited settings?

Objective: To compare virologic success between adult patients on tenofovir (TDF) and zidovudine (AZT)-containing first-line antiretroviral (ART) regimens in 10 rural clinics in Lesotho, Southern Africa.

Methods: Multicentre cross-sectional study, patients ≥16 years, on first-line ART ≥6 months, receiving AZT/lamivudine (3TC) or TDF/3TC combined with efavirenz (EFV) or nevirapine (NVP). Patient characteristics and clinical/therapeutic history were collected on the day of blood draw for viral load (VL). Analysis was stratified for non-nucleoside reverse transcriptase inhibitor (EFV or NVP). A logistic regression model weighted for patients' baseline characteristics was used to assess the likelihood of virologic success (<80 copies/ml) in patients with TDF- as compared to AZT-backbones.

Results: In total 1539 patients were included in the analysis. Most were clinically and immunologically stable (clinical failure: 2.7% (AZT) and 2.8% (TDF); immunological failure: 4.6% (AZT) and 4.8% (TDF)). In EFV-based regimens (n = 1162), TDF was significantly associated with higher rates of virologic suppression than AZT (93.8% vs. 88.1%; weighted odds ratio: 2.15 (95% CI: 1.29-3.58; P = 0.003)). In NVP-based regimens, a similar trend was observed, but not significant (89.4% vs. 86.7%; 1.99 (0.83-4.75, P = 0.121)).

Conclusion: These findings support the WHO recommendation to use TDF/3TC/EFV as first-line regimen. They do, however, not support the recommendation that patients who are clinically stable on AZT should continue on this first-line regimen.