Trichomonads Test · Stool

More than half of people who carry a trichomonad infection feel nothing at all. The parasite can live quietly in the vagina, urethra, or urinary tract for months or years, spreading to partners and raising the risk of other serious health problems, all while a standard pelvic exam or wet mount microscopy slide looks unremarkable.

This test looks for trichomonads, most often Trichomonas vaginalis (the species responsible for the common sexually transmitted infection called trichomoniasis). Detecting it matters because the infection is strongly linked to HIV acquisition, adverse pregnancy outcomes, and cervical disease, and because it can be fully cured with a single course of oral antibiotics once found.

What the Test Is Looking For

Trichomonads are microscopic, single-celled parasites called protozoa. The species most relevant to human health is Trichomonas vaginalis (TV), which infects the urogenital tract in both women and men. Two other species, Pentatrichomonas hominis and Dientamoeba fragilis, can show up in stool testing and mostly live in the intestines, where they are usually harmless but can occasionally cause diarrhea.

Modern testing uses nucleic acid amplification tests (NAATs), which detect the parasite's genetic material. This matters because older methods like wet mount microscopy miss a large share of infections. In pooled clinical data, wet mount microscopy caught roughly 31 to 65 percent of infections, while NAATs caught 95 to 100 percent. A result is reported simply as detected or not detected, not as a numeric level.

Why This Infection Matters

Trichomoniasis is likely the most common non-viral sexually transmitted infection worldwide, with more than 150 million new cases globally each year. Most infections produce no symptoms, which is why it spreads easily and why people discover it only when they decide to test for it.

HIV Acquisition

Trichomonas infection is associated with roughly 1.5 times the risk of acquiring HIV compared with people who do not have it. The inflammation the parasite causes in the genital tract appears to create an easier entry point for HIV, which is one reason diagnosis and treatment of trichomoniasis is considered a tool for reducing new HIV infections.

Cervical Disease and Cancer

Large meta-analyses link trichomonad infection to a higher risk of cervical neoplasia (abnormal cell growth that can lead to cervical cancer). In a pooled analysis of roughly 470,000 women, trichomonas-positive women showed higher risk of cervical carcinogenesis. In a separate large population study of women with HPV16 (the highest-risk strain of human papillomavirus), co-infection with trichomonas further raised the risk of cervical intraepithelial neoplasia grade 2 to 3, which is a precancerous lesion.

Pregnancy Outcomes

Trichomoniasis during pregnancy is associated with preterm delivery, prelabour rupture of membranes, and low birthweight infants. A classic prospective study of 13,816 pregnant women found that those infected at mid-gestation were significantly more likely to deliver preterm and to have low-birthweight infants compared to uninfected women.

Male Reproductive Health

Men are rarely screened despite high infection rates among partners of infected women. A population-based case-control study of 250,176 people found that men diagnosed with trichomoniasis had a significantly higher risk of benign prostatic hyperplasia (a non-cancerous enlargement of the prostate) and prostate cancer. Evidence across other studies on prostate cancer risk is mixed, but partner transmission back to women makes male testing a public health issue even when symptoms are absent.

How Results Are Reported

Unlike cholesterol or blood sugar, trichomonads are not reported as a number. The result is binary: the parasite is either detected or not detected. There are no risk tiers, no optimal ranges, and no quantitative cutpoints. Any detection is considered a true positive that warrants treatment.

These research-based detection performance numbers come from comparative diagnostic studies using specimens from both symptomatic and asymptomatic men and women. Different labs and platforms report slightly different values, so the numbers below are illustrative orientation rather than universal guarantees. The takeaway is that the testing method matters enormously for whether you find an infection or miss it.

Source: Pooled results across studies including Gaydos 2017, Nye 2009, Schwebke 2011, Huppert 2007, and Van Der Pol 2021.

What this means for you: if you are relying on a wet mount slide from an office visit, a negative result is not reassuring. A NAAT is the right test if you want a real answer, and it can be performed on a vaginal swab or urine sample.

When Results Can Be Misleading

A negative result from a lower-sensitivity test does not rule out infection. If you tested with wet mount microscopy and the result was negative, but you have symptoms or a partner with a known infection, retesting with a NAAT is the correct next step.

Sample type also matters. For women, vaginal swabs (including self-collected ones) are the most sensitive specimen, with pooled sensitivity around 98 percent for detecting trichomonads. Urine samples are acceptable but slightly less sensitive. For men, first-catch urine is standard.

Tracking Over Time and What to Do After a Positive Result

Because this is an infection and not a chronic metric, trending it means retesting to confirm cure rather than watching a trajectory. After treatment, repeat positive results are common. In one randomized trial comparing single-dose versus 7-day metronidazole in women, the 7-day regimen produced significantly fewer repeat positive tests, and guidelines now favor the multi-dose regimen for women.

You should retest roughly three months after treatment, even if symptoms resolved. This catches both treatment failure and, more commonly, reinfection from an untreated partner.

Decision Pathway for a Positive Result

A positive trichomonad result should prompt four actions. First, get treated with the guideline-recommended regimen (covered in the interventions section). Second, make sure your sexual partners are tested and treated; partner treatment rates in studies show that a majority of male partners are infected and almost all are asymptomatic. Third, consider testing for other sexually transmitted infections, since co-infection with chlamydia, gonorrhea, bacterial vaginosis, or HIV is common enough that most modern panels test for multiple pathogens simultaneously. Fourth, if you are pregnant or trying to conceive, discuss results with your obstetric provider given the links to preterm delivery.

If you are HIV-positive, annual retesting is recommended because trichomoniasis is more common and harder to clear in this population, and because the two infections amplify each other's risks.

Who Should Test

Guidelines support testing for people with genital symptoms, HIV-positive women, partners of infected individuals, pregnant women with risk factors, and anyone in a high-prevalence setting such as an STD clinic or correctional facility. Studies in abortion clinics found that testing only symptomatic patients would miss 98 percent of infections, which is why universal testing in high-prevalence settings has been shown to be feasible and effective. If you have had a new partner, multiple partners, or a partner with an unknown sexual history, testing is reasonable even if you feel fine.