Table 2

Cox regression analysis of hospitalizations with pelvic inflammatory disease by previous C. trachomatis infection

Prior infections

No. of women*

Observation years

No. of events

Incidence rate per 100 person-years

(95% CI)

Adjusted† hazard ratio (95% CI)

None

20,534

169,192

143

0.08 (0.07–0.10)

Reference

One or more

4,413

32,057

48

0.15 (0.11–0.20)

1.69 (1.21–2.37)

* Number of women at end of follow-up period

† Adjusted for age at first test

Bakken and Ghaderi BMC Infectious Diseases 2009 9:130   doi:10.1186/1471-2334-9-130