ABSTRACT
Background: Zidovudine (AZT) is a common component of antiretroviral therapy (ART) in resource-limited settings. However, AZT is associated with myelotoxity that often presents with anaemia. The aim of this study was to determine the incidence of anaemia among patients initiated on AZT-containing and non-AZT containing ART regimens.
Methods: In this retrospective analysis, records from 800 ART-naïve HIV-infected patients were abstracted by simple random sampling from program databases. Rates of anaemia were compared between patients initiated on AZT- versus non- AZT-containing ART regimens. Patients were stratified according to absence (Group A) or presence (Group B) of baseline anaemia defined as haemoglobin < 10.5g/dl. Incidence was calculated as total cases of AZT-induced anaemia (group A) or worsening of anaemia (group B) during the study period divided by person-time at risk and adjusted per 100 person-years. Average time-to-event and survival curve were estimated using Kaplan Meier survival analysis.
Results: In group A (without baseline anaemia), the incidence of anaemia in the AZT-exposed versus non-exposed cohorts was 73.3 and 17.6 per 100 patient years at 6 months, and 60.5 and 8.5 per 100 patient years at 12 months, respectively. In group B, the incidence of worsening anaemia was 65.9 and 26.2 per 100 patient years at 6 months, and 57.5 and 17.9 per 100 patient years after 12 months in AZT-exposed and AZT-unexposed cohorts, respectively. The estimated time to event (developing anaemia) was 2.3 (1.5 – 3.4) months, while estimated to event (worseninig anaemia) was 2.0 (1.5 – 4.0).
Conclusions: HIV-infected patients initiated on AZT-containing ART are 2.7 and 4.5 more likely to develop anaemia at 6 and 12 months, respectively, compared to those initiating a non-AZT containing regimen. When censored at 12 months the overall incidence of AZT-related anaemia was estimated at 22.3% (38.2 incidences per person years). Majority (75%) of the AZT-related anaemia occurred early with estimated time-to-event occurring within the first 3.8 months