Characterizing a Leak in the HIV Care Cascade: Assessing Linkage Between HIV Testing and Care in Tanzania

Disease progression and mortality with untreated HIV infection: evidence synthesis of HIV seroconverter cohorts, antiretroviral treatment clinical cohorts and population-based survey data

Introduction

Model‐based estimates of key HIV indicators depend on past epidemic trends that are derived based on assumptions about HIV disease progression and mortality in the absence of antiretroviral treatment (ART). Population‐based HIV Impact Assessment (PHIA) household surveys conducted between 2015 and 2018 found substantial numbers of respondents living with untreated HIV infection. CD4 cell counts measured in these individuals provide novel information to estimate HIV disease progression and mortality rates off ART.

Methods

We used Bayesian multi‐parameter evidence synthesis to combine data on (1) cross‐sectional CD4 cell counts among untreated adults living with HIV from 10 PHIA surveys, (2) survival after HIV seroconversion in East African seroconverter cohorts, (3) post‐seroconversion CD4 counts and (4) mortality rates by CD4 count predominantly from European, North American and Australian seroconverter cohorts. We used incremental mixture importance sampling to estimate HIV natural history and ART uptake parameters used in the Spectrum software. We validated modelled trends in CD4 count at ART initiation against ART initiator cohorts in sub‐Saharan Africa.

Results

Median untreated HIV survival decreased with increasing age at seroconversion, from 12.5 years [95% credible interval (CrI): 12.1–12.7] at ages 15–24 to 7.2 years (95% CrI: 7.1–7.7) at ages 45–54. Older age was associated with lower initial CD4 counts, faster CD4 count decline and higher HIV‐related mortality rates. Our estimates suggested a weaker association between ART uptake and HIV‐related mortality rates than previously assumed in Spectrum. Modelled CD4 counts in untreated people living with HIV matched recent household survey data well, though some intercountry variation in frequencies of CD4 counts above 500 cells/mm³ was not explained. Trends in CD4 counts at ART initiation were comparable to data from ART initiator cohorts. An alternate model that stratified progression and mortality rates by sex did not improve model fit appreciably.

Conclusions

Synthesis of multiple data sources results in similar overall survival as previous Spectrum parameter assumptions but implies more rapid progression and longer survival in lower CD4 categories. New natural history parameter values improve consistency of model estimates with recent cross‐sectional CD4 data and trends in CD4 counts at ART initiation.

How does HIV testing modality impact the cascade of care among persons diagnosed with HIV in Ethiopia?

Background

Despite scaling up of HIV programmes in sub-Saharan Africa, many people living with HIV (PLHIV) are unaware of their HIV status. New testing modalities, such as community-based testing, can improve test uptake, but it is uncertain whether type of testing modality affects the subsequent cascade of HIV care.

Objective

To compare linkage to care and antiretroviral treatment (ART) outcomes with regard to type of HIV testing modality.

Methods

A retrospective registry-based study was conducted at public ART clinics in an urban uptake area in Central Ethiopia. Persons aged ≥15 years newly diagnosed with HIV in 2015–2018 were eligible for inclusion. Data on patient characteristics and testing modality were analysed for associations with the following outcomes: ART initiation, retention in care at 12 months after starting ART, and viral suppression (<1000 copies/ml, recorded during the first 12 months after ART initiation), using uni- and multivariable analysis. Separate analyses disaggregated by sex were performed.

Results

Among 2885 included PLHIV (median age 32 years, 59% female), 2476 (86%) started ART, 1422/2043 (70%) were retained in care, and 953/1046 (92%) achieved viral suppression. Rates of ART initiation were lower among persons diagnosed through community-based testing (adjusted odds ratio [AOR] 0.44, 95% confidence interval [CI] 0.29–0.66) and among persons diagnosed through provider-initiated testing (AOR 0.65, 95% CI 0.44–0.97) compared with facility-based voluntary counselling and testing. In sex-disaggregated analyses, community-based testing was associated with lower rates of ART initiation among both women and men (AOR 0.47, 95% CI 0.27–0.82; AOR 0.39, 95% CI 0.19–0.78, respectively). No differences were found for retention in care or viral suppression with regard to test modality.

Conclusion

Type of HIV testing modality was associated with likelihood of ART initiation, but not with subsequent treatment outcomes among persons starting ART.