title: Formulas for estimating the costs averted by sexually transmitted infection (STI) prevention programs in the United States.
abstract: BACKGROUND
  Sexually transmitted infection (STI) prevention programs can mitigate the health and economic burden of STIs. A tool to estimate the economic benefits of STI programs could prove useful to STI program personnel.
  
  
  METHODS
  We developed formulas that can be applied to estimate the direct medical costs and indirect costs (lost productivity) averted by STI programs in the United States. Costs and probabilities for these formulas were based primarily on published studies.
  
  
  RESULTS
  We present a series of formulas that can be used to estimate the economic benefits of STI prevention (in 2006 US dollars), using data routinely collected by STI programs. For example, the averted sequelae costs associated with treating women for chlamydia is given as (Cw)(0.16)(0.925)(0.70)($1,995), where Cw is the number of infected women treated for chlamydia, 0.16 is the absolute reduction in the probability of pelvic inflammatory disease (PID) as a result of treatment, 0.925 is an adjustment factor to prevent double-counting of PID averted in women with both chlamydia and gonorrhea, 0.70 is an adjustment factor to account for the possibility of re-infection, and $1,995 is the average cost per case of PID, based on published sources.
  
  
  CONCLUSIONS
  The formulas developed in this study can be a useful tool for STI program personnel to generate evidence-based estimates of the economic impact of their program and can facilitate the assessment of the cost-effectiveness of their activities.
authors.affiliation: Division of STD Prevention, National Center for HIV/AIDS, Viral Hepatitis, STD, and TB Prevention, Centers for Disease Control and Prevention, Atlanta, Georgia, USA. hbc7@cdc.gov
authors.forename: Harrell W
authors.initials: HW
authors.lastname: Chesson
authors.forename: Dayne
authors.initials: D
authors.lastname: Collins
authors.forename: Kathryn
authors.initials: K
authors.lastname: Koski