Reasons for first line ART modification over the years during the ART scale up in Uganda

BACKGROUND: During the initial scale up of ART in sub-Saharan Africa, prescribed regimens included drugs with high potential for toxicity (particularly stavudine). More recently a growing number of patients requires second line treatment due to treatment failure, especially following the expansion of viral load testing. We aim to determine the reasons and risk factors for modification of first line ART across the years. METHODS: We included patients started on standard first line ART (2NRTI + 1 NNRTI) between 2005 and 2016 at the Infectious Diseases Institute, Kampala, Uganda. We described the reasons for treatment modification categorized in (1) toxicity (2) treatment failure (3) other reason (new TB treatment, new pregnancy). We used Cox proportional hazard to identify factors associated with treatment modification due to toxicity. RESULTS: We included 14,261 patients; 9114 (63.9%), were female, the median age was 34 years (IQR: 29-40), 60.8% were in WHO stage 3 and 4. The median BMI and CD4 count were 21.9 (IQR: 19.6-24.8) and 188 cell/µL (IQR: 65-353) respectively; 27.5% were started on stavudine, 46% on zidovudine, and 26.5% on a tenofovir containing regimens. We observed 6248 ART modifications in 4868/14,261 patients (34.1%); 1615 were due to toxicity, 1077 to treatment failure, 1330 to contraindications, and 1860 patients following WHO recommendation of phasing out stavudine and substituting with another NRTI. Modification for drug toxicity declined rapidly after the phase out of stavudine (2008), while switches to second line regimes increased after the implementation of viral load monitoring (2015). Patients with normal BMI compared to underweight, (HR: 0.79, CI 0.69-0.91), with CD4 counts 200-350 cells/µL compared to < 200 cells/µL (HR: 0.81- CI 0.71-0.93), and started on zidovudine (HR: 0.51 CI 0.44-0.59) and tenofovir (HR: 0.16, CI 0.14-0.22) compared to stavudine were less likely to have ART modification due to toxicity. Older patients (HR: 1.14 per 5-year increase CI 1.11-1.18), those in WHO stage 3 and 4 (HR: 1.19, CI 1.06-1.34) were more likely to have ART modification due to toxicity. CONCLUSIONS: Toxicity as reason for drugs substitution decreased over time mirroring the phase out of stavudine, while viral load expansion identified more patients in need of second line treatment.