A trichomonas test detects Trichomonas vaginalis, a common sexually transmitted parasite that infects an estimated 3.7 million people in the United States. The test typically involves a vaginal swab or urine sample, and the most accurate version, called a nucleic acid amplification test (NAAT), catches about 97% of infections. No special preparation is needed before the test.
How the Test Works
There are three main ways to test for trichomoniasis, and they differ significantly in accuracy.
The gold standard is a NAAT, which detects the parasite’s genetic material. NAATs have a sensitivity of 96.7% and specificity of 97.5%, meaning they catch nearly all true infections and rarely produce false results. This is the method the CDC recommends.
An older approach is wet-mount microscopy, where a clinician places a sample on a slide and looks for the moving parasite under a microscope. This method is cheap and gives results within minutes, but it only catches 44% to 68% of infections. That means it misses roughly a third to half of people who actually have trichomoniasis. If your provider uses this method and the result is negative but you still have symptoms, a NAAT follow-up is worth requesting.
Culture testing, which involves growing the parasite in a lab over several days, was once considered the best option. Its sensitivity ranges from 44% to 75%, better than microscopy in some cases but far below what NAATs achieve.
What Happens During the Test
For women, the test uses a vaginal swab. A clinician or the patient inserts a soft-tipped swab about two inches into the vagina, gently rotates it for 10 to 30 seconds so it absorbs moisture from the vaginal walls, then places it in a transport tube. Vaginal swabs are preferred over cervical swabs for NAAT testing, and self-collected swabs are just as reliable as clinician-collected ones. If you’re offered the option to collect your own sample in a private room, the results will be equally accurate.
For men, urine is the standard specimen. You provide a “first-catch” sample, meaning the initial stream of urine rather than a midstream collection. Research has also shown that self-collected swabs from the opening of the urethra can actually detect more infections than urine alone, though urine remains the most commonly used specimen in clinical settings.
No special preparation is required before a trichomonas test. You don’t need to fast, avoid medications, or abstain from sexual activity beforehand.
When to Get Tested
If you’ve been exposed to trichomoniasis or have symptoms like unusual discharge, itching, burning, or discomfort during urination, the timing of your test matters. Testing at one week after exposure catches most infections. Waiting until about four weeks after exposure catches nearly all of them. If you test too early, the parasite may not be present in high enough numbers to detect, even with a NAAT.
Many people with trichomoniasis have no symptoms at all, which is why screening guidelines exist for certain groups. The CDC recommends considering screening for women in high-prevalence settings like STI clinics, as well as women with multiple sexual partners, a history of STIs, or other risk factors. Women living with HIV should be screened at least once a year. There is no routine screening recommendation for men or for the general population.
Understanding Your Results
A positive result means Trichomonas vaginalis was detected in your sample. Trichomoniasis is curable with prescription antibiotics, and both you and your sexual partner will need treatment to prevent reinfection.
A negative result means the parasite was not found. With a NAAT, a negative result is highly reliable. With microscopy, a negative result is less reassuring, particularly if you have symptoms. In one clinical trial, four urine specimens came back negative on a NAAT despite the patients having confirmed infections through other methods. False negatives are uncommon with NAATs but not impossible, especially with urine samples from women (vaginal swabs are more reliable for female patients).
False positives are also rare. In the same trial, about 0.8% of samples showed discordant results, and when those were retested with additional molecular methods, many of the apparent false positives turned out to be true infections that the older reference tests had missed.
Why the Test Type Matters
If you’re being tested for trichomoniasis, it’s worth asking which method your provider uses. The difference between a 50% detection rate (microscopy) and a 97% detection rate (NAAT) is enormous. Many clinics have shifted to NAATs, and some now offer combination panels that test for chlamydia, gonorrhea, and trichomoniasis from a single sample. But microscopy is still used in settings where cost or speed is prioritized, and a negative result from that method alone should not be considered definitive if you have symptoms or a known exposure.