“Trich vag by NAA” is a lab test that checks for trichomoniasis, a common sexually transmitted infection caused by a tiny parasite called Trichomonas vaginalis. “NAA” stands for nucleic acid amplification, a technology that detects the parasite’s genetic material in a sample from your body. If you’re seeing this on lab paperwork, it means your provider ordered (or your results came from) one of the most accurate tests available for diagnosing trich.
What the Test Actually Does
A nucleic acid amplification test, or NAAT, works by finding and copying tiny fragments of the parasite’s RNA in your sample. Even if only a very small number of parasites are present, the test amplifies their genetic signal until it’s detectable. This makes NAATs far more sensitive than older methods. The traditional approach, called a wet mount, involves placing a drop of vaginal fluid on a slide and looking for moving parasites under a microscope. That method catches only about 60% of infections. NAATs, by contrast, have sensitivity ranging from 96% to 100% depending on the specific platform used, with specificity (the ability to correctly rule out infection) above 99%.
In practical terms, a wet mount misses roughly 4 out of every 10 infections. A NAAT misses almost none. That’s why the CDC considers NAATs the preferred method for diagnosing trichomoniasis.
How the Sample Is Collected
For women, the preferred sample is a swab from the vagina or cervix. Your provider can collect this during a pelvic exam, or in many cases you can collect a vaginal swab yourself. Urine samples also work. For men, the test typically uses a urine sample or a urethral swab. At-home collection kits are available through some providers and testing services, where you collect a urine or vaginal fluid sample and mail it to a lab.
No special preparation is needed. You don’t have to fast or stop medications beforehand.
What Your Results Mean
Results come back as either “detected” (positive) or “not detected” (negative). A positive result means the parasite’s genetic material was found in your sample, confirming an active trichomoniasis infection. A negative result means no parasite RNA was found, which reliably rules out infection given the test’s high accuracy.
One thing to keep in mind: symptoms can take 5 to 28 days to appear after exposure, and some people never develop symptoms at all. So a positive result doesn’t necessarily mean you’ll feel anything wrong. Many people with trich have no discharge, itching, or discomfort. That’s one reason testing matters, because you can carry and spread the infection without knowing it.
Who Should Get Tested
There are no blanket screening recommendations for the general population. However, testing is recommended in several situations:
- Vaginal discharge: Anyone seeking care for unusual discharge should be tested.
- High-risk settings: Annual screening may be appropriate for people seen in STI clinics or correctional facilities, or for those with multiple sexual partners, a history of STIs, or substance use concerns.
- HIV-positive women: Routine annual screening is recommended because trichomoniasis can worsen HIV-related outcomes.
Your provider may also order this test alongside other STI panels, since trich is frequently tested at the same time as chlamydia and gonorrhea using similar sample types.
Treatment After a Positive Result
Trichomoniasis is curable with antibiotics. The standard treatment is a course of metronidazole taken twice daily for seven days. When sticking to a week-long regimen is difficult, a single larger dose of metronidazole or tinidazole can be used instead. Both sexual partners need treatment at the same time, even if only one person tested positive. Otherwise, reinfection is almost guaranteed.
You should avoid alcohol while taking these medications, as the combination can cause nausea and vomiting. Most people feel no side effects beyond mild stomach upset.
Follow-Up Testing
The CDC recommends retesting three months after treatment to check for repeat infection. This isn’t because the antibiotics failed. It’s because reinfection from an untreated partner or a new exposure is common. NAAT is the preferred method for this follow-up test, again because of its superior accuracy. For women living with HIV, retesting at three months is especially important and specifically recommended in clinical guidelines.
Retesting too soon after treatment (within a few weeks) can sometimes pick up residual genetic material from dead parasites, producing a false positive. The three-month window avoids this problem while also catching any new infections early.