# Table 1 Parameter values describing the natural history of chlamydia infection, PID development and the screening intervention

Parameters Baseline values Explanation Sensitivity analysis Source
Distribution Parameters
Model parameters
λ   Force of infection (per day), calculated using*
1/r 365 Mean duration of infection (days) [6, 16] N(μ,σ2) μ=365 σ2=752 Consensus
p 5.7% Prevalence at baseline  Bin(n,p) n=2519 $\text{p}=\frac{143}{2519}$ 
α   Effective testing rate (per day), calculated using
c 22.2% Coverage of testing uptake (per year)  Bin(n,p) n=2377 $\text{p}=\frac{527}{2377}$ 
δ 8.0% Treatment failure  U(a,b) a=0% b=50% Consensus
f estimated Fraction of women becoming infected with chlamydia who will develop PID
Input parameter
x 30.0% Proportion of PID cases due to chlamydia in control group  Bin(n,p) n=23 $\text{p}=\frac{7}{23}$ 
1. *In the absence of the tria (α=0), to observe chlamydia prevalence p at steady state: $\lambda =\frac{p}{1-p}r$.
2. Reported uptake of chlamydia testing c during the follow-up period (outside of the trial) is reduced by the proportion with treatment failure δ, which results in the effective testing rate $\alpha =\frac{-ln\left(1-\left(1-\delta \right)c\right)}{365}$ per day .
3. N(μ,σ2), normal distribution (mean, variance); Bin(n,p), binomial distribution (size, probability); U(a,b), uniform distribution (minimum, maximum). 