Table 1:

Model parameters

ParameterExpected valueProbability distribution*Source
Clinical parameters
Prevalence of maternal infection, %10
 Chlamydia1.90Dirichlet (40, 2, 2, 2178)
 Coinfection with chlamydia and gonorrhea0.10
 No maternal infection97.90
Prenatal STI screening results, %8
 False positive4.13Dirichlet (33, 1, 12, 754)
 False negative0.12
 True positive1.50
 True negative94.25
Probability of ON in infant exposed to maternal infection, %
 Chlamydia15.00Beta (156, 899)11
 Gonorrhea40.00Beta (3688, 5531)4
Risk of ON treatment failure and blindness, %
 Chlamydia14.30Beta (326, 1850)11
 Gonorrhea3.46Beta (145, 4045)12
Relative risk of ON with prophylactic erythromycin ointment
 ON caused by gonorrhea0.19LogNormal (0.07, 0,50)13
 ON caused by chlamydia0.93LogNormal (0.48, 1.79)14
Probability of adverse events of prophylaxis, %10Beta (127, 1142)15,16
Cost parameters, $
Erythromycin ON prophylaxis0.90Fixed17
Adverse events from prophylaxis33.70Fixed18
Gonococcal ON2871.10Gamma (179.44, 16)8
Chlamydia ON574.47Gamma (35.90, 16)8
Blindness19 370.00Gamma (4842.50, 16)19
Utility values
Healthy term infant0.876Normal (0.876, 0.045)14
Healthy, aged ≥ 12+ yr0.912–0.699Fixed20
Disutility from blindness, aged 0–16 yr0.329Normal (0.329, 0.036)14
Disutility from blindness, adult0.208Normal (0.208, 0.013)21
  • Note: ON = ophthalmia neonatorum, STI = sexually transmitted infection.

  • * Dirichlet (α, β, γ, δ) relates to a Dirichlet distribution, where α, β, γ and δ represent the number of individuals with the inclusive events. Beta (α, β) relates to a beta distribution, where α represents the number of individuals with events and β represents the number of those without events. Gamma (α, β) relates to a gamma distribution, where α represents the shape and β represents the scale. Normal (α, β) relates to a normal distribution, where α represents the mean and β represents the standard error. LogNormal (α, β) relates to a log normal distribution, where α represents the 2.5 percentile and β represents the 97.5 percentile.