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 [11]	Bin(n,p)	n=2519	$\text{p}=\frac{143}{2519}$	[11]
α		Effective testing rate (per day), calculated using†
c	22.2%	Coverage of testing uptake (per year) [11]	Bin(n,p)	n=2377	$\text{p}=\frac{527}{2377}$	[11]
δ	8.0%	Treatment failure [17]	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 [11]	Bin(n,p)	n=23	$\text{p}=\frac{7}{23}$	[11]

^*In the absence of the tria (α=0), to observe chlamydia prevalence p at steady state: $\lambda =\frac{p}{1-p}r$.

^†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 [18].

N(μ,σ²), normal distribution (mean, variance); Bin(n,p), binomial distribution (size, probability); U(a,b), uniform distribution (minimum, maximum).