Epidemiology and predictors of repeat positive chlamydia tests: the Brant County cohort, Ontario, Canada

ObjectivesRepeat positive tests for chlamydia (CR) may help explain current high rates of chlamydia despite years of screening, partner notification and treatment to reduce sequelae. We wanted to determine the numbers of CRs over time as a proportion of all chlamydia cases, and define the differences in demographic, clinical, behavioural, and public health management indicators, between individuals who have experienced a CR and individuals who experienced a single infection in Brant County, Ontario. MethodsA retrospective cohort was developed using notifiable disease data extracted from the integrated public health system. Cases were laboratory confirmed chlamydia and gonorrhea infections in Brant County between January 1st, 2006 and December 31st, 2015. During the study period, 3,499 chlamydia cases and 475 gonorrhea cases were diagnosed. The total number of individuals with chlamydia in that period was 3,060, including 157 coinfections with gonorrhea. Differences between those with reinfection and those with single infection were evaluated using univariate and multivariate (Cox proportional hazards model) methods. ResultsFour hundred and ninety-nine (16.30%) individuals experienced CR 28 days from initial infection; of which 328 (65.73%) occurred within 2 years and 211 (42.28%) within 1 year. The median time to CR was 276 days, consistent with existing Canadian literature. Independent risk factors for CR included being male, 25 years old or younger, and not receiving recommended treatment for initial and/or subsequent infection. ConclusionsThese findings suggest that inadequate treatment play a significant role in CR, while accounting for young age and male gender, likely due to untreated sex partners. Key MessagesO_LISixteen percent of people experienced a second positive chlamydia test more than 28 days after their initial positive test in a cohort of 3,499 patients C_LIO_LIThose who had a second positive test were more likely to be male, younger than 25 and had not received recommended antimicrobials C_LIO_LIConfirmation of any kind of partner notification was missing in 88% of records C_LI