A cohort-based approach to the HIV treatment cascade finds linkage the major bottleneck

From HIV infection to therapeutic response: a population-based longitudinal HIV cascade-of-care study in KwaZulu-Natal, South Africa.

Haber N, Tanser F, Bor J, Naidu K, Mutevedzi T, Herbst K, Porter K, Pillay D, Barnighausen T. Lancet HIV. 2017 Jan 30. pii: S2352-3018(16)30224-7. doi: 10.1016/S2352-3018(16)30224-7. [Epub ahead of print]

Background: Standard approaches to estimation of losses in the HIV cascade of care are typically cross-sectional and do not include the population stages before linkage to clinical care. We used individual-level longitudinal cascade data, transition by transition, including population stages, both to identify the health-system losses in the cascade and to show the differences in inference between standard methods and the longitudinal approach.

Methods: We used non-parametric survival analysis to estimate a longitudinal HIV care cascade for a large population of people with HIV residing in rural KwaZulu-Natal, South Africa. We linked data from a longitudinal population health surveillance (which is maintained by the Africa Health Research Institute) with patient records from the local public-sector HIV treatment programme (contained in an electronic clinical HIV treatment and care database, ARTemis). We followed up all people who had been newly detected as having HIV between Jan 1, 2006, and Dec 31, 2011, across six cascade stages: three population stages (first positive HIV test, HIV status knowledge, and linkage to care) and three clinical stages (eligibility for antiretroviral therapy [ART], initiation of ART, and therapeutic response). We compared our estimates to cross-sectional cascades in the same population. We estimated the cumulative incidence of reaching a particular cascade stage at a specific time with Kaplan-Meier survival analysis.

Findings: Our population consisted of 5205 individuals with HIV who were followed up for 24 031 person-years. We recorded 598 deaths. 4539 individuals gained knowledge of their positive HIV status, 2818 were linked to care, 2151 became eligible for ART, 1839 began ART, and 1456 had successful responses to therapy. We used Kaplan-Meier survival analysis to adjust for censorship due to the end of data collection, and found that 8 years after testing positive in the population health surveillance, 16% had died. Among living patients, 82% knew their HIV status, 45% were linked to care, 39% were eligible for ART, 35% initiated ART, and 33% had reached therapeutic response. Median times to transition for these cascade stages were 52 months, 52 months, 20 months, 3 months, and 9 months, respectively. Compared with the population stages in the cascade, the transitions across the clinical stages were fast. Over calendar time, rates of linkage to care have decreased and patients presenting for the first time for care were, on average, healthier.

Interpretation: HIV programmes should focus on linkage to care as the most important bottleneck in the cascade. Cascade estimation should be longitudinal rather than cross-sectional and start with the population stages preceding clinical care.

Abstract access   [1]

Editor’s notes: The HIV treatment cascade outlines the stages required to effectively treat HIV, starting with HIV testing and ending with viral suppression. The cascade has become a widely-used framework to evaluate the performance of HIV care programmes, to measure progress towards universal treatment coverage, and to identify gaps in care. However, methods for constructing the HIV treatment cascade vary considerably. The majority of cascade analyses rely on cross-sectional data obtained from different sources. The authors present the first analysis of the HIV treatment cascade that follows individuals longitudinally from the time of HIV infection across all stages of the cascade. By linking data from a demographic surveillance system with electronic clinical records, they are able to describe the cascade for a large population-based cohort of people living with HIV in rural KwaZulu-Natal, South Africa.  They demonstrate that, once people became eligible for ART, the rates of ART initiation, and of viral suppression after initiation, were high. Half of individuals started ART within three months of becoming eligible, and 94% of people on therapy achieved virologic suppression. In addition, retention in care improved over time. However, a key finding is that rates of HIV diagnosis and linkage to care worsened over time, and less than 50% of people had linked to care within eight years of HIV infection, despite 82% being aware of their status. As illustrated by cascade analyses in other settings, increasing linkage to care remains a major challenge for reaching the UNAIDS 90-90-90 treatment target in sub-Saharan Africa.  

In addition to highlighting linkage as the most important bottleneck in the HIV care cascade in this part of rural KwaZulu-Natal, the study illustrates some of the weaknesses in traditional cascade analyses based on cross-sectional data. The cross-sectional cascade is constructed from snapshots of different groups of people in a particular moment in time, rather than describing what happens to the same group of people over time. The authors illustrate how a cross-sectional analysis can give a misleading impression of improvement in the cascade over time, because it fails to take account of changes in the population. The longitudinal cascade, by following the same group of people, provides important insights into the true progression of the cascade over time, and identification of losses along each stage. However, the individual-level longitudinal data necessary for this type of analysis requires a large investment in data collection, and is unlikely to be feasible in most resource-limited settings.

Africa [6]
South Africa [7]
  • [8]