Indirect effects of HIV differentiated service delivery programmes on quality of clinic care: a retrospective cohort study of clients starting antiretroviral therapy

Introduction In countries with high HIV prevalence, differentiated service delivery programmes (DSD) for antiretroviral therapy (ART) play a vital role in improving access to ART for people living with HIV (PLHIV). While the benefits of DSD for clients enrolled in these programmes have been described, it is unknown whether DSD additionally benefits clients who are ineligible for these programmes, through allowing more clinic resources to be directed towards them. We aimed to assess whether increases in DSD referrals are associated with better care for clients initiating ART. Methods De-identified, routinely collected TIER.Net data from 112 clinics in KwaZulu-Natal, South Africa were used to assess service delivery for clients initiated during 2022-2023. Outcomes were the probability of newly-initiated clients having an initiation CD4 count result, a 6-month viral load result (among those visiting at 6 months) and being retained for 6 months after initiation (<90 days late for all visits). Using generalized linear mixed effects models, we measured the association of clinic DSD referral with outcomes and derived marginal probabilities for each outcome for varying DSD levels. Risk differences were calculated, with confidence intervals estimated using bootstrapping. Results Between August 2022 and October 2023, 26,226 PLHIV with a median age of 32 years were initiated on ART. Monthly DSD referral proportions at the clinics varied but increased on average from 21% in August 2022 to 29% in October 2023. Overall, 77% of clients had a CD4 count test at initiation, 72% of those attending their 6-month visit had a viral load test, and 70% were retained to 6 months. We found a positive relationship between DSD referrals and test completion, although this association was only weakly significant for viral load test; when DSD referrals increased from 20-30%, the probability of having a CD4 count and viral load test increased by 0.97% (95% CI: -0.27,2.58%) and 1.35% (95% CI: 0.11,2.95%) respectively. We found no evidence of an association with DSD referrals and 6-month retention. Conclusions In the first study of this topic, increases in DSD resulted in small improvements in care. With full DSD scale-up, however, programmatically meaningful effects could be achieved.