Background: Routine reporting of sexually transmitted infections (STIs) in Iran is one of the main information sources on STIs, endures some diminution under influence of several factors. We aimed to adjust registered STI data with a model-based approach and estimate the incidence and prevalence of STIs in Iran.
Methods: In this cross-sectional study, we developed a stochastic compartmental model considering effects of influential factors on STI reporting process to adjust registered STI data. We reviewed literature and used Delphi method to collect data and estimate model parameters. We calibrated the model using Monte Carol simulation with 95% confidence interval (CI). Finally, we validated the models by comparing their output with investigational data.
Results: The estimated prevalence of male urethral discharge was 0.40% (95% CI: 0.26%, 0.65%); the prevalence of genital ulcers was 3.68% (95% CI: 2.31%, 6.43%) in women and 0.16% (95% CI: 0.10%, 0.27%) in men. The estimated incidence for Neisseria gonorrhoeae, Chlamydia trachoma and syphilis per 1000 women was 2.44 (95% CI: 1.17, 6.65), 5.02 (95% CI: 2.78, 10.16) and 0.04 (95% CI: 0.02, 0.05) respectively; the corresponding figures per 1000 men were 0.43 (95% CI: 0.26, 0.80), 0.82 (95% CI: 0.42, 1.92) and 0.005 (95% CI: 0.003, 0.008).

Conclusions: Various factors are responsible for the obvious underestimation in the number of STIs registered in Iran. Notwithstanding this underestimation, our models offer an indirect method of estimating the prevalence of STIs in the country. Providing policymakers and STI experts with more realistic estimates might prompt policymakers and STI experts to recognize the importance of STIs in Iran and help them to develop appropriate prevention and control programs.