Retesting and repeat positivity following diagnosis of Chlamydia trachomatis and Neisseria gonorrhoea in New Zealand: a retrospective cohort study

BACKGROUND: Testing for reinfection at 3 to 6 months following treatment for Chlamydia Trachomatis or Neisseria gonorrhoea is recommended in best practice sexual health management guidelines. This study aimed to describe rates of retesting and repeat positivity following diagnosis of chlamydia or gonorrhoea in a defined geographic region of New Zealand. METHODS: Retrospective cohort study in Wellington, New Zealand involving analysis of laboratory data for chlamydia and gonorrhoea tests performed in primary care and sexual health clinics (July 2012–July 2015). Outcome measures: rate of retesting and rate of repeat positivity 6 weeks to 6 months after a positive result (index event). Kaplan-Meier curves were used to plot time from first index event to retest. Logistic regression modelling was used to determine the odds of retesting and repeat positivity between 6 weeks and 6 months of follow-up, adjusting for potential confounders (age, gender, ethnicity and socioeconomic deprivation). RESULTS: Overall 29.4% (1919/6530) of the cohort was retested between 6 weeks and 6 months, with 18% (347/1919) of those retested returning positive results. Lower odds of retesting were observed for males (OR 0.4, 95% CI 0.34–0.48), and individuals of NZ Maori (OR 0.72, 0.61–0.85) and Pacific ethnicities (OR 0.49, 0.39–0.62, reference European). Factors associated with higher odds of repeat positivity on retesting included male gender (OR 2.0, 1.14–2.82), age 15–19 years (OR 1.78, 1.32–2.41, reference 20–24 years), chlamydia/gonorrhoea co-infection (OR 2.39, 1.32–4.35, reference chlamydia only), Maori (OR 1.6, 1.18–2.17) and Pacific ethnicities (OR 1.88, 1.22–2.9, reference European). CONCLUSIONS: We observed low adherence to STI retesting guidelines, and marked gender and ethnic disparities in rates of retesting and repeat positivity. Low retesting rates are suggestive of low levels of awareness of this aspect of patient management, and an absence of a systematic approach to retesting. High rates of repeat positivity reinforce the importance of advising patients about reducing their risk of reinfection, including notification and treatment of all recent sexual partners. Greater priority needs to be placed on increasing retesting and reducing rates of reinfection, with strategies implemented to improve these important aspects of patient care and population STI control.