Aim Studies have demonstrated and quantified the relationship between chlamydia infection and pelvic inflammatory disease (PID). However there is relatively little information regarding the rate of PID following gonorrhoea infection. This analysis compares the rate of hospitalisation for PID following a diagnosis of gonorrhoea to the rate following a chlamydia diagnosis.

Method All women, aged 15–45 years, in New South Wales (NSW), with a diagnosis of chlamydia or gonorrhoea between 1/7/2000 and 31/12/2008 were followed for up to one year after diagnosis for hospitalisations for PID. The incidence rates of PID hospitalisation among women with a chlamydia or gonorrhoea diagnosis were compared to the whole of the NSW population using standardised incidence ratios (SIRs). Poisson regression was used to compare the rates of PID hospitalisation after adjusting for age, diagnosis date, socioeconomic group, area of residence and prior births.

Results There were 38379 women with a chlamydia diagnosis. During 35014 person years of follow-up (PYFU), 485 were hospitalised for PID; incidence rate (IR) 13.8 per 1000 PYFU (95% CI 12.6–15.1). Among 1023 women with a gonorrhoea diagnosis, during 895 PYFU 45 were hospitalised for PID; (IR 50.3 per 1000 PYFU, 95% CI 35.6–65.0). Compared to the age-equivalent NSW female population, the incidence of PID hospitalisation was 27.0 (95% CI 24.4–29.8) times greater among women who had a chlamydia diagnosis in the year prior to hospitalisation and 95.8 (95% CI 64.2–137.6) times greater among women with a gonorrhoea diagnosis. Younger age, diagnosis prior to 2005, socioeconomic disadvantage and prior births were also associated with an increased rate of PID hospitalisation.

Conclusion Hospitalisation rates for PID were over 3 times greater in women diagnosed with gonorrhoea than chlamydia, and rates in both were substantially higher than in the general female population. Our results suggest that gonorrhoea causes more serious reproductive health sequelae than chlamydia.