Positivity and Risk Factors for Trichomonas Vaginalis Among Women Attending a Sexual Health Clinic in Melbourne, 2006-2019

Background: Trichomonas vaginalis is not a notifiable disease in Australia in most states, resulting in limited Australian epidemiological studies. This study aimed to examine the positivity of T. vaginalis in women attending the Melbourne Sexual Health Centre (MSHC) and identify associated factors.

Methods: All women aged ≥16 years who were tested for T. vaginalis at MSHC from 2006-2019 were included. The diagnostic method changed from culture to nucleic acid amplification test (NAAT) in August 2018. The annual positivity of T. vaginalis was calculated. Due to the data completeness, we performed a generalised estimating equations multivariable logistic regression using data from 2011-2019 to examine factors associated with T. vaginalis positivity.

Results: From 2006-2019, 69,739 tests for T. vaginalis were conducted, and 294 tested positive (0.42%, 95% CI 0.37-0.47). Approximately 60% of women tested reported symptoms. After adjusting for potential confounders including the change in diagnostic method, there was a 21% (95% CI 12-31%) annual increase in T. vaginalis positivity between 2011 and 2019. Women with concurrent syphilis had the highest odds of testing positive for T. vaginalis (aOR 21.55; 95% CI 6.96-66.78); followed by women who had injected drugs in the last 12 months (aOR 6.99; 95% CI 4.11-11.87), were aged ≥35 years (aOR 3.47; 95% CI 2.26-5.35), or with concurrent chlamydia (aOR 1.77; 95% CI 1.05-2.99).

Conclusion: The rising positivity of T. vaginalis at MSHC irrespective of change in diagnostic method suggests a concurrent community-wide rise in Melbourne. Given the rising positivity, testing informed by risk factors should be considered.