Increased diagnostic yield of routine multiplex PCR compared to clinician requested testing for detection of Trichomonas vaginalis

Trichomonas vaginalis (TV) infection is the leading cause of non-viral sexually transmitted infection (STI) globally and is endemic in rural and remote Australia. However, current accurate prevalence data for TV in urban Australia are scarce as TV is not a notifiable infection outside of the Northern Territory (NT). This study evaluated Australian guidelines for TV testing and determined TV prevalence among patients at a large urban public hospital in Melbourne, Australia. A retrospective analysis of genitourinary samples screened for STIs by multiplex polymerase chain reaction (MPCR) between May 2017 and April 2019 was performed. A total of 7155 results (5064 females) were included in the analysis. A prevalence for TV of 1.7% (n=123) was found, which was higher than Neisseria gonorrhoeae (1.4%, n=103) but less than Chlamydia trachomatis (5%, n=358). The highest rate of TV (3%) was found in females aged 30-44 years (n = 48). Routine MPCR improved TV detection almost six-fold compared with clinician request based testing. Current targeted testing guidelines for TV were inadequate for case finding in an urban setting, and clinical request among symptomatic patients was rare. MPCR testing provides a comprehensive testing strategy for curable STI, and removes the need for clinical suspicion of TV. Implementation of MPCR for STI screening can improve TV detection in populations not normally suspected to be at risk and therefore potentially reduce disease transmission or complications associated with undiagnosed infection.

Supplemental Trichomonas vaginalis testing is required to maintain control following a transition from Pap smear to HPV DNA testing for cervical screening: a mathematical modelling study

Objectives

Using mathematical modelling, we have previously shown that the prevalence of infection with Trichomonas vaginalis (TV) is likely to increase in the general population in Australia with the transition from Pap smear-based cervical screening to human papillomavirus (HPV) DNA testing. Here we use the existing model to estimate the level of supplemental testing required to maintain TV control.

Methods

A compartmental mathematical model describing the transmission of TV in the general heterosexual population in Australia was used to evaluate the impact of a range of screening scenarios on TV prevalence over time following the transition to HPV DNA testing for cervical screening. Scenarios considered were the inclusion of a TV test with the HPV test and the addition of TV testing to routine chlamydia testing conducted in primary care.

Results

Our modelling suggests that with sufficient coverage, inclusion of TV testing with routine chlamydia screening in general practice, TV prevalence can be reduced over time, but at the current reported coverage will gradually increase following the transition to HPV testing. Inclusion of TV testing with HPV testing in the cervical screening programme is preferable to no supplemental testing but is considerably less effective in controlling TV.

Conclusions

These findings support the inclusion of TV testing with routine chlamydia testing of young people.

Impact of replacing cytology with human papillomavirus testing for cervical cancer screening on the prevalence of Trichomonas vaginalis: a modelling study

Objectives

Trichomonas vaginalis (TV) is the most common curable STI worldwide and is associated with increased risk of HIV acquisition and serious reproductive morbidities. The prevalence of TV infection is very low in Australian cities, and this is thought to be at least partly due to incidental detection and treatment of TV in women participating in the cervical cytology screening programme. In 2017, the national cervical screening programme will transition to a new model based on testing for high-risk (HR) human papillomavirus (HPV), with a reduced frequency and commencement at an older age. We model the potential impact of this transition on TV prevalence in Australia.

Methods

A mathematical model was developed to describe the transmission of TV in the general population and used to evaluate scenarios that capture the switch from cytology-based screening to HR HPV testing. Under these scenarios, individuals with asymptomatic TV who test negative for HR HPV will remain undiagnosed and untreated. We estimate the change in TV prevalence expected to occur due to the switch from cytology to HR HPV testing and changes to the frequency and age at commencement of screening.

Results

Our results suggest that with the transition to HR HPV testing, TV prevalence may increase from the current ~0.4% to 2.8% within 20 years if TV testing coverage is not increased and HR HPV prevalence does not decline further. If HR HPV prevalence continues to decline at its current rate with ongoing vaccination, TV prevalence is predicted to increase to 3.0% within this time frame.

Conclusions

Our modelling suggests that in a setting like Australia, where TV can be detected incidentally through cytology-based cervical screening, a transition to HPV testing is likely to result in increasing TV prevalence over time unless additional measures are implemented to increase TV testing and treatment.