Trends of reported chlamydia infections and related complications in New Zealand, 1998-2008

Aim: To compare trends in chlamydia (Chlamydia trachomatis) testing and detection with trends in hospital discharge rates of chlamydia-related diseases in the upper North Island of New Zealand during 1998-2008. Methods: Analysis of trends in chlamydia testing and detection rates and age-specific hospital admission rates per 100 000 females for pelvic inflammatory disease (PID), female infertility and ectopic pregnancy, and per 100 000 males for epididymo-orchitis. Results: Regional laboratory testing volumes increased from 3732 tests per 100 000 population in 1998 to 9801 tests per 100 000 in 2008. Two of three regions had a significant increase in percent test positivity over time. The highest detection rates and greatest increase in reported cases were amongst women aged 15-24 years, at 1992 per 100 000 in 1998, to 5737 per 100 000 in 2008. For women aged 15-24 years, the rate of hospital admissions for PID and chlamydia-related pelvic infections declined during 1998-2004 but rose in 2005-08, the rate of publicly-funded infertility admissions fell and the ectopic pregnancy rate was unchanged. The age-specific rate for epididymo-orchitis admissions amongst 15-44-year-old men remained stable. Conclusion: Chlamydia testing volumes from three New Zealand regions have trebled since 1998, as have reported infection rates, although disease complication rates do not appear to have increased. Test positivity increases may reflect better targeted testing of those more at risk or a rising chlamydia incidence. The recent rise in hospital admissions for PID among women aged 15-24 is a concern; ongoing monitoring of these trends, despite data limitations, is important.