Table 2. Summary of risk estimates.

	Manitoba, Canada	Denmark Chlamydia Study	UK-based POPI-RCT
			Deferred screening	Screened
Prevalence of chlamydia (95% CI)	5.48% (5.31–5.65)	4.32% (3.65–4.99)	5.93% (4.63–7.23)	5.42% (4.17–6.68)
Observed rate of PID per 100,000 women by 12-months	2086.04	890.16	1598.96~	1346.07~
Incidence of PID in chlamydia positive (95% CI)	5.27% (4.59–6.00)	1.28% (1.21–1.35)	9.46% (2.79–16.13)	1.59% (0.00–8.53)
Incidence of PID in chlamydia-negative (95% CI)	1.90% (1.80–2.00)	0.67% (0.63–0.71)	1.34% (0.91–1.91)*
Relative risk (95% CI)	2.77 (2.41–3.20)	1.92 (1.78–2.08)	7.06 (3.21–15.55)	1.19 (1.64–8.55)
Attributable risk	3.37	0.61	8.12	0.25
Attributable risk %	63.95%	48.01%	85.84%	15.63%
Population excess fraction (95% CI)	8.86% (7.15–10.75)	3.84% (3.26–4.41)	26.44% (11.57–46.32)	0.99% (0.00–29.06)
Crude number of cases attributed to baseline chlamydia in cohort of tested women (study size)	134 (72,883)	98 (286,223)	6 (1270)**	0.1 (1259)**
Number of cases attributed to baseline chlamydia per 100,000 tested women	184	34	484	13

~Data not available to allocate PID incidence in chlamydia-negative women to the two study arms therefore combined chlamydia-negative data used in calculation

*Data not available to calculate separately

**Assumption that incidence of PID in chlamydia-negative women is 1.34%.