Improvements in Spectrum's fit to program data tool.

Area of Science:

• Epidemiology
• Public Health
• Biostatistics

Background:

• The Joint United Nations Program on HIV/AIDS (UNAIDS) Spectrum software is crucial for global HIV epidemic monitoring.
• HIV incidence trends are typically derived from seroprevalence data or program/vital registration data.
• Existing methods in Spectrum have limitations, particularly when surveillance data is scarce.

Purpose of the Study:

• To describe the development and application of the Fit to Program Data (FPD) tool.
• To provide an improved method for estimating HIV incidence trends using program data.
• To enhance HIV epidemic monitoring in countries with robust program data but limited seroprevalence data.

Main Methods:

• The FPD tool models HIV incidence using simple or double logistic functions.
• Function parameters are estimated using historical program data (newly diagnosed HIV cases, deaths).
• Maximum likelihood estimation or minimum chi-squared distance methods are employed, with uncertainty estimation.

Main Results:

• The FPD tool was applied to 62 countries in the 2016 UNAIDS estimates round.
• Both maximum likelihood and minimum chi-squared methods yielded comparable results.
• A double logistic curve fit most countries, with a simple logistic curve suitable for the remainder.

Conclusions:

• The FPD tool provides a simpler and improved approach for estimating HIV incidence.
• It is particularly valuable for middle- and high-income countries with strong program data.
• This method enhances the ability to monitor HIV epidemics where seroprevalence data is limited.