Incidence and predictors of annual chlamydia testing among 15–29 year olds attending Aboriginal primary health care services in New South Wales, Australia

Simon Graham, Rebecca J. Guy, James S. Ward, John Kaldor, Basil Donovan, Janet Knox, Debbie McCowen, Patricia Bullen, Julie Booker, Chris O’Brien, Kristine Garrett, Handan C. Wand

For the past two decades, chlamydia has been the most commonly notified infectious disease among young people (15-29 year olds) in Australia, the United States of America and the United Kingdom and rates have increased annually in these three countries. In Australia, rates of chlamydia are three times higher in Aboriginal compared with non-Aboriginal people. Australian sexually transmissible infection guidelines recommend annual chlamydia testing for 15-29 year old females and males. This analysis will examine the incidence and predictors of annual chlamydia testing in 15-29 year olds attending four Aboriginal Community Controlled Health Services (ACCHS) in Australia. From 2009-2011, attendance and chlamydia testing data were extracted from the patient system to calculate the number and proportion of 15-29 year olds that were tested for chlamydia and that tested positive for chlamydia by gender (male, female), age-group (15-19, 20-24, 25-29 years), Aboriginal status (Aboriginal, non-Aboriginal people) and by the four ACCHSs sites (1, 2, 3 and 4). A cohort was created to calculate the incidence rate per 100 person-years (PY) and predictors of an annual chlamydia test (a test within 12-months of a previous test/visit) by the above factors using Cox regression. Unadjusted and adjusted hazard ratios (AHR) and their 95 % confidence intervals (CIs) and p-values were calculated with significance at p < 0.05. From 2009-2011, there were 2896 individuals who attended the four ACCHSs. Overall , 17 % (22 % of females and 10 % of males) were tested for chlamydia and 9 % tested positive (8 % of females and 14 % of males). The median time to an annual chlamydia test was 10.7 months. The cohort included 2318 individuals. Overall the incidence rate of an annual chlamydia test was 9.1 per 100 PY (11.6 in females and 5.8 in males). Predictors of an annual chlamydia test were being female (AHR: 1.7, 95 % CI: 1.2-2.2, p < 0.01), being 15-19 years old (AHR: 1.6, 95 % CI: 1.1-2.3, p < 0.01) and attending ACCHS site 2 (AHR: 3.8, 95 % CI: 1.8-8.0, p < 0.01). This analysis highlights that opportunistic STI testing strategies are needed to increase annual chlamydia testing in young people; especially males.