Trichomoniasis is a common sexually transmitted infection (STI) caused by the microscopic parasite Trichomonas vaginalis. While routine testing is common for other STIs, diagnosing trichomoniasis can seem less straightforward. This article clarifies why trichomoniasis is not always routinely tested for, examining diagnostic methods, testing considerations, and when testing is performed. It also explores the potential health implications of an undiagnosed infection.
How Trichomoniasis Is Diagnosed
Diagnosing trichomoniasis involves identifying the Trichomonas vaginalis parasite in a genital fluid sample. Wet mount, a traditional method, examines a fluid sample under a microscope for motile parasites. While quick and inexpensive, wet mounts have lower sensitivity, detecting the infection in only 51% to 65% of cases.
Rapid antigen tests detect specific parasite proteins, providing results within minutes. These tests show improved sensitivity (78% to 90%) compared to wet mounts. Nucleic acid amplification tests (NAATs) are the most sensitive and specific diagnostic method.
NAATs detect the parasite’s genetic material, offering 92-100% sensitivity and 95-100% specificity. These tests can be performed on urine samples or vaginal swabs, even when parasite levels are low.
Factors Influencing Routine Testing Decisions
Several factors explain why trichomoniasis is not universally included in standard STI screening. Testing methodologies play a role; NAATs, while accurate, are often more expensive and require specialized laboratory equipment than simpler tests for other common STIs. This contrasts with blood tests for HIV or syphilis, or less complex urine tests for chlamydia and gonorrhea.
Most individuals (70% to 85%) with trichomoniasis experience no symptoms. When symptoms occur, they can be mild or non-specific, resembling other vaginal or urinary tract infections. This asymptomatic nature limits the effectiveness of symptom-based screening.
Public health priorities also guide screening, often focusing on STIs with more severe, irreversible long-term health consequences. Infections like HIV and syphilis can lead to life-threatening conditions or significant complications if untreated. Public health efforts prioritize preventing these outcomes.
Economic considerations also influence routine screening programs. Widespread screening for an infection that is curable with antibiotics and often asymptomatic involves substantial costs. The cost-effectiveness of mass screening for trichomoniasis is debated, balancing the expense of sensitive tests against the overall public health benefit compared to targeted testing.
When Trichomoniasis Testing is Indicated
While not routinely tested for in all general health screenings, specific circumstances prompt trichomoniasis testing. Testing is indicated if an individual experiences symptoms like unusual vaginal discharge, itching, burning, or painful urination. Symptoms can appear 5 to 28 days after infection, or much later.
Testing is also advised if a sexual partner has been diagnosed, even without symptoms, to prevent reinfection and further spread. Pregnant individuals may be tested, particularly if symptomatic or at high risk for STIs.
Populations with a higher STI prevalence, such as individuals with multiple sexual partners or those in correctional facilities, may have more frequent testing. Trichomoniasis testing may also be part of a broader STI workup when other STIs are diagnosed.
Potential Health Impacts of Undiagnosed Trichomoniasis
Leaving trichomoniasis undiagnosed and untreated can lead to health complications. The infection’s inflammation can increase the risk of acquiring or transmitting other STIs, including HIV. Studies suggest trichomoniasis can increase a woman’s HIV acquisition risk by approximately 1.5 times.
For pregnant individuals, untreated trichomoniasis can contribute to adverse pregnancy outcomes, including increased risk of premature birth and low birth weight. While rare, transmission to the newborn during vaginal birth can occur.
In women, undiagnosed trichomoniasis can lead to pelvic inflammatory disease (PID), an infection of the reproductive organs that can result in chronic pelvic pain or infertility. Men may experience urethritis (urethra inflammation) or prostatitis (prostate gland inflammation).