Model parameters
| Parameter | Expected value | Probability distribution* | Source |
|---|---|---|---|
| Clinical parameters | |||
| Prevalence of maternal infection, % | 10 | ||
| Chlamydia | 1.90 | Dirichlet (40, 2, 2, 2178) | |
| Gonorrhea | 0.20 | ||
| Coinfection with chlamydia and gonorrhea | 0.10 | ||
| No maternal infection | 97.90 | ||
| Prenatal STI screening results, % | 8 | ||
| False positive | 4.13 | Dirichlet (33, 1, 12, 754) | |
| False negative | 0.12 | ||
| True positive | 1.50 | ||
| True negative | 94.25 | ||
| Probability of ON in infant exposed to maternal infection, % | |||
| Chlamydia | 15.00 | Beta (156, 899) | 11 |
| Gonorrhea | 40.00 | Beta (3688, 5531) | 4 |
| Risk of ON treatment failure and blindness, % | |||
| Chlamydia | 14.30 | Beta (326, 1850) | 11 |
| Gonorrhea | 3.46 | Beta (145, 4045) | 12 |
| Relative risk of ON with prophylactic erythromycin ointment | |||
| ON caused by gonorrhea | 0.19 | LogNormal (0.07, 0,50) | 13 |
| ON caused by chlamydia | 0.93 | LogNormal (0.48, 1.79) | 14 |
| Probability of adverse events of prophylaxis, % | 10 | Beta (127, 1142) | 15,16 |
| Cost parameters, $ | |||
| Erythromycin ON prophylaxis | 0.90 | Fixed | 17 |
| Adverse events from prophylaxis | 33.70 | Fixed | 18 |
| Gonococcal ON | 2871.10 | Gamma (179.44, 16) | 8 |
| Chlamydia ON | 574.47 | Gamma (35.90, 16) | 8 |
| Blindness | 19 370.00 | Gamma (4842.50, 16) | 19 |
| Utility values | |||
| Healthy term infant | 0.876 | Normal (0.876, 0.045) | 14 |
| Healthy, aged ≥ 12+ yr | 0.912–0.699 | Fixed | 20 |
| Disutility from blindness, aged 0–16 yr | 0.329 | Normal (0.329, 0.036) | 14 |
| Disutility from blindness, adult | 0.208 | Normal (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.