Key input parameters.

ART – antiretroviral therapy; HIV – human immunodeficiency virus; HCV – hepatitis C virus; ORT – opioid replacement therapy; CMS – Center for Medicare and Medicaid Services; CPT4 - Current Procedural Terminology, 4th Edition.*The proportion of the population that is IDU and the HIV prevalence among IDUs was estimated as the unweighted average of the 21 Metropolitan Statistical Areas (MSAs) with populations between 1.5 and 5 million. Across these cities there is very wide variation in both parameters, so we performed extensive sensitivity analysis on these inputs. The cities included were (Population; % of population that are IDU; Prevalence of HIV in IDU): Boston–Brockton–Nashua, MA–NH (4.2 million, 1.6%, 4.5%), Washington, DC–MD–VA–WV (3.6 million, 0.8%, 9.0%), Philadelphia, PA–NJ (3.4 million, 1.7%, 8.8%), Atlanta, GA (3.0 million, 0.5%, 14.9%), Houston, TX (3.0 million, 1.1%, 6.4%), Detroit, MI (3.0 million, 0.9%, 6.4%), Dallas, TX (2.6 million, 1.3%, 3.4%), Phoenix–Mesa, AZ (2.3 million, 1.2%, 3.6%), Riverside–San Bernardino, CA (2.3 million, 0.9%, 3.5%), Minneapolis, MN (2.1 million, 0.5%, 3.3%), Orange County, CA (2.0 million, 1.0%, 2.4%), San Diego, CA (2.0 million, 1.3%, 3.4%), Nassau–Suffolk, NY (1.8 million, 0.7%, 12.3%), St. Louis, MO–IL (1.8 million, 0.6%, 3.1%), Baltimore, MD (1.7 million, 3.4%, 11.7%), Seattle–Bellevue–Everett, WA (1.7 million, 1.6%, 2.9%), Oakland, CA (1.7 million, 1.3%, 4.2%), Tampa–St. Petersburg–Clearwater, FL (1.6 million, 1.1%, 6.1%), Miami, FL (1.5 million, 0.6%, 22.8%), Denver, CO (1.5 million, 1.4%, 3.1%), Pittsburgh, PA (1.5 million, 0.9%, 3.9%), Cleveland–Lorain–Elyria, OH (1.5 million, 0.8%, 4.2%). We excluded the three MSAs with populations over 5 million: Los Angeles–Long Beach, CA (6.5 million, 1.5%, 3.8%), New York, NY (6.4 million, 1.4%, 21.2%), Chicago, IL (5.7 million, 0.6%, 8.4%).