Updates to Spectrum's case surveillance and vital registration tool for HIV estimates and projections

Abstract

Introduction: The Case Surveillance and Vital Registration (CSAVR) model within Spectrum estimates HIV incidence trends from surveillance data on numbers of new HIV diagnoses and HIV-related deaths. This article describes developments of the CSAVR tool to more flexibly model diagnosis rates over time, estimate incidence patterns by sex and age group and by key population group.

Methods: We modelled HIV diagnosis rate trends as a mixture of three factors, including temporal and opportunistic infection components. The tool was expanded to estimate incidence rate ratios by sex and age for countries with disaggregated reporting of new HIV diagnoses and AIDS deaths, and to account for information on key populations such as men who have sex with men (MSM), males who inject drugs (MWID), female sex workers (FSW) and females who inject drugs (FWID). We used a Bayesian framework to calibrate the tool in 71 high-income or low-HIV burden countries.

Results: Across countries, an estimated median 89% (interquartile range [IQR]: 78%-96%) of HIV-positive adults knew their status in 2019. Mean CD4 counts at diagnosis were stable over time, with a median of 456 cells/μl (IQR: 391-508) across countries in 2019. In European countries reporting new HIV diagnoses among key populations, median estimated proportions of males that are MSM and MWID was 1.3% (IQR: 0.9%-2.0%) and 0.56% (IQR: 0.51%-0.64%), respectively. The median estimated proportions of females that are FSW and FWID were 0.36% (IQR: 0.27%-0.45%) and 0.14 (IQR: 0.13%-0.15%), respectively. HIV incidence per 100 person-years increased among MSM, with median estimates reaching 0.43 (IQR: 0.29-1.73) in 2019, but remained stable in MWID, FSW and FWID, at around 0.12 (IQR: 0.04-1.9), 0.09 (IQR: 0.06-0.69) and 0.13% (IQR: 0.08%-0.91%) in 2019, respectively. Knowledge of HIV status among HIV-positive adults gradually increased since the early 1990s to exceed 75% in more than 75% of countries in 2019 among each key population.

Conclusions: CSAVR offers an approach to using routine surveillance and vital registration data to estimate and project trends in both HIV incidence and knowledge of HIV status.

Keywords: HIV case-based surveillance; HIV incidence; HIV-related mortality; key population; knowledge of status; statistical models.

Figure 1

Intercompartmental flow describing diagnosis uptake. All parameters related to HIV diagnosis and incidence are estimated by the model. Other rates, such as antiretroviral therapy (ART) recruitment (adjusted for ART discontinuation), demographic parameters governing entry in the model at 15 years of age and both natural and HIV‐related mortality are informed by Spectrum.

Figure 2

Selected incidence models and incidence rates among adults 15–49 years. (a) Number of countries using each incidence model. The x‐axis indicates the regions and the y‐axis indicates the number of times each incidence model was selected by region. (b) Median incidence rate (solid lines) and interquartile ranges (shaded regions) by UNAIDS region. The x‐axis indicates the calendar year and the y‐axis indicates incidence rate in person‐years expressed as percentage. AP, Asian Pacific; CAR, Caribbean; EECA, Eastern Europe and central Asia; LA, Latin America; MENA, Middle East and North Africa; WCENA, Western and central Europe and North America.

Figure 3

Mean CD4 at diagnosis and proportion of people living with human immunodeficiency virus (PLHIV) aware of their HIV status by sex and UNAIDS region. (a) Median and interquartile ranges (IQR) of mean CD4 at diagnosis. (b) Median and IQR of proportion of PLHIV aware of their HIV status. Each panel represents one of the UNAIDS region. The medians are represented with solid lines and IQR are represented by shaded regions. The x‐axes indicate the calendar year and the y‐axes indicate the mean CD4 at diagnosis (a) or knowledge of HIV status among HIV‐infected individuals (b). AP, Asian Pacific; CAR, Caribbean; EECA, Eastern Europe and central Asia; LA, Latin America; MENA, Middle East and North Africa; WCENA, Western and central Europe and North America.

Figure 4

Estimated and projected trends of indicators in Europe. (a) proportions of key populations; (b) HIV incidence; (c) HIV prevalence; (d) mean CD4 at diagnosis among these populations; (e) knowledge of HIV status for those living with HIV. Each panel represents a key population group. FSW, female sex workers; FWID, females who inject drugs; MSM, men who have sex with men; MWID, males who inject drugs. The x‐axes indicate calendar year, and y‐axes indicate the indicator of interest. The solid lines represent the median across countries and the greyed areas indicate the interquartile ranges. Only countries reporting to The European Surveillance System (TESSy) were included in the analysis.