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Trichomonas


At a Glance

Why Get Tested?

To diagnose an infection with the parasite Trichomonas vaginalis, which causes the sexually transmitted disease trichomoniasis

When to Get Tested?

When a woman has symptoms of infection, such as a foul-smelling vaginal discharge, genital itching, and/or pain during urination, or when a man has genital itching or irritation, burning after urination or ejaculation, and/or a discharge from the urethra

Sample Required?

In women, a swab of vaginal or cervical secretions; in men, a urethral swab. In some cases, urine may be tested.

Test Preparation Needed?

None

The Test Sample

What is being tested?

Testing can detect an infection with Trichomonas vaginalis, a microscopic, single cell (protozoan) parasite that is usually transmitted sexually, causing vaginal infections in women and urethral infections (urethritis) and prostatitis in men.

According to the Centers for Disease Control and Prevention (CDC), trichomoniasis, which is caused by the infection, is the most common, curable sexually transmitted disease (STD). In the U.S., an estimated 3.7 million people have the infection, but only about 30% develop any symptoms. Symptoms are more common in women than in men.

Trichomonas vaginalis is one of the most common causes of vaginitis (inflammation of the vagina) in women. When they occur, symptoms include:

  • Vaginal swelling
  • Itching, irritation, soreness
  • Burning sensation
  • Frothy, yellow-green vaginal discharge
  • Foul-smelling vaginal discharge
  • Frequent urge to urinate
  • Possible blood-spotting

In men, symptoms may include:

  • Burning after urinating or ejaculating
  • Itching or irritation of the urethra
  • Discharge from the urethra

These symptoms may take 5 to 28 days after exposure to an infected person or longer to develop; however, once diagnosed, trichomoniasis is easily treated with prescription antibiotics. During treatment, an infected person should cease sexual activity and inform partners so that they can also be treated and prevent re-infection.

How is the sample collected for testing?

In women, a swab of secretions is collected from the vagina. The sample may be obtained from the same thin-layer collection vial used for a Pap smear. In men, a swab is inserted into the urethra. Urine samples may also be used.

Is any test preparation needed to ensure the quality of the sample?

No test preparation is needed.

The Test

How is it used?

The test is used to diagnose an infection with the parasite Trichomonas vaginalis (T. vaginalis). Secretions from the vagina (for women) or urethra (for men) are tested by one of the following methods:

  • Wet prep. A direct microscopic examination of the secretions for the presence of the parasitic cells may determine if someone's symptoms are caused by an infection with T. vaginalis.The wet prep is performed on secretions that are freshly obtained and examined promptly under the microscope without the aid of any special stains.
  • Culture. This test is very sensitive and specific but requires up to 7 days to allow sufficient numbers of the parasite to grow and be detected. The CDC recommends culture of vaginal samples from women in whom trichomoniasis is suspected but not confirmed by wet prep.
  • Molecular testing. Using direct DNA probes or PCR (polymerase chain reaction) technology offers the most sensitive and timely determination, usually within 24 hours. Samples from women can be obtained during a routine gynecologic examination that includes a Pap smear. An FDA-cleared PCR test approved for detection of gonorrhea and chlamydial infection has been modified to include detection ofT. vaginalis in vaginal or endocervical swabs from women and in urine from both women and men.
  • Other methods. These include the direct fluorescent antibody (DFA) test and a test that detects trichomonas antigens.

When is it ordered?

A doctor may order a test for T. vaginalis when someone complains of symptoms, such as (for women) vaginal itching, burning, a foul-smelling vaginal discharge or (for men) pain on urination or discharge from the urethra.

If someone has an infection with another sexually transmitted disease, the doctor might order the test as well. Likewise, if results indicate that a person is infected with T. vaginalis, the person may also be tested for chlamydia and gonorrhea since these STDs often occur together.

What does the test result mean?

A positive test indicates an active infection with T. vaginalis that requires treatment with a course of prescription medication. If someone is infected, their sexual partner(s) should also be tested and treated as well.

A negative test means either there is no infection with T. vaginalis or the parasite was not able to be detected in the sample using the method performed. If trichomoniasis is still suspected, another method may be used to confirm the result.

Is there anything else I should know?

An infected person is at greater risk of getting other sexually transmitted diseases. The genital inflammation that occurs with trichomoniasis can increase a woman's susceptibility to HIV infection and to pelvic inflammatory disease.

Neonatal trichomoniasis, though rare, can occur, causing complications in the newborn.

Fecal contamination of the specimen may show a non-pathogenic organism (Pentatrichomonas hominis, formally known as Trichomonas hominis) that is similar in appearance and may be confused with T. vaginalis through direct observation. The presence of this organism does not require treatment.



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