Table. Model Parameters, Data Type Used to Inform Parameters, and Sampling Distributions for Probabilistic Sensitivity Analyses.
| Parameters | Data typesa | PSA distributionb |
|---|---|---|
| Cohort characteristics among people experiencing homelessness who inject drugs | ||
| Background mortality | National homeless, US Census | |
| Infection prevalence based on injection frequency | National inject, primary national inject, US Census | |
| Injection frequency stratified by age | City | |
| Proportion male | City | |
| Male age (mean/SD) | City | Normal |
| Female age (mean/SD) | City | Normal |
| Minimum age (mean/SD) | US Census | Normal |
| Needle sharing prevalence | City | Uniform |
| Skin cleaning prevalence | City | Uniform |
| Sequelae of drug use parameters | ||
| Combined overdose prevalence (high) | National inject, national homeless, primary national homeless | Uniform |
| Combined overdose prevalence (low) | National injection, national homeless, primary national homeless | Uniform |
| Fatal overdose prevalence | National inject, national homeless | Uniform |
| IE prevalence | National inject | Uniform |
| Overdose history multipliers | National inject | Uniform |
| Infection history multiplier | National inject | Uniform |
| Mortality, untreated SSTI | National inject | Uniform |
| Mortality, inpatient SSTI | National inject | Uniform |
| Mortality, untreated IE | National inject | Uniform |
| Mortality, inpatient IE | National inject | Uniform |
| Mortality, inpatient overdose | National inject | Uniform |
| Inpatient parameters | ||
| Inpatient linkage (SSTI) | National inject | Uniform |
| Inpatient linkage (IE) | National inject | Uniform |
| Inpatient linkage (overdose) | National inject | Uniform |
| Discharge against medical advice | National inject | Uniform |
| Inpatient SSTI duration (mean/STD) | National inject | |
| Inpatient IE duration (mean/SD) | National inject | |
| Outpatient parameters | ||
| Linkage from inpatient to outpatient, with MOUD | National inject | Uniform |
| Background linkage to outpatient care | National inject | Uniform |
| MOUD acceptance | City, primary national homeless | Uniform |
| Unlinkage from care, with MOUD | National inject, national homeless | Uniform |
| Unlinkage from care, without MOUD | National inject, national homeless | Uniform |
| Transition probabilities | ||
| Injection frequency transition probabilities | National inject, national homeless, primary national inject | Uniform |
| Needle sharing transition probabilities | National inject, primary national homeless | Uniform |
Abbreviations: IE, infective endocarditis; MOUD, medications for opioid use disorder; SSTI, skin and soft tissue infection.
Data types were defined as follows: city, primary data from 2018 National HIV Behavioral Surveillance data on people who inject drugs and people experiencing homelessness in the last year from each of the 23 US cities being analyzed; national inject, data specific to people who inject drugs from published literature; national homeless, data specific to people experiencing homelessness from published literature; primary national inject, primary data from cohort studies, randomized clinical trials, and case-control studies about people who inject drugs processed to develop input parameters; primary national homeless, primary data from cohort studies, randomized clinical trials, case-control studies about people experiencing homelessness processed to develop input parameters; and US Census, primary data from US Census processed to develop input parameters.
Probabilistic sensitivity analysis (PSA) was performed to characterize parameter uncertainty and create credible intervals for outcome estimates. The model was programmed to utilize normal, uniform, and log-normal distributions for PSA. Parameters with empty cells in the PSA distribution column were not included in the probabilistic sensitivity analysis.