Chlamydia retesting and retest positivity rates: results from a state-wide laboratory data linkage study in Tasmania, 2012-13

Background: Chlamydia re-infection increases the likelihood of adverse long-term sequelae. Clinical guidelines recommend retesting at 3-12 months for individuals with positive results, to detect re-infections. Retesting and test positivity levels were measured in young people who previously tested positive for chlamydia infection.

Methods: All chlamydia tests conducted during 2012-13 in Tasmanian residents aged 15-29 years were linked. Retesting and retest positivity rates were calculated by sex, age, socioeconomic indicators and test timeframe.

Results: Retesting rates were higher in females than males at 3 months (14.5%, n=242/1673 vs 10%, n=71/721) (P<0.01) and 12 months (27%, 265/968 vs 24%, 98/410) (P=0.24). The retesting rate was higher in females living in areas of most disadvantage (35.5%, 154/434) compared with areas of middle and least disadvantage (26% 139/534) (P<0.01). Males were more likely than females to retest positive at 3 months (35%, 25/71 vs 23%, 55/242) (P<0.01); retest positivity at 12 months was 32% in both sexes (males 98/140; females 265/968). Retest positivity was higher in males living in areas of least disadvantage (43%, 3/7) compared with middle (24%, 16/67) (P=0.27) and most (27%, 10/37) (P=0.09); and higher in females living in areas of least disadvantage (39%, 7/18) compared with middle (24%, 29/121) (P<0.01) and most (31%, 48/154) (P=0.02).

Conclusions: Retesting rates are low in Tasmania and retest positivity is high, reinforcing the importance of promoting safer sex practices, partner notification and treatment, and retesting.