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Trichomonas

Also known as: Trichomonas vaginalis; T. vaginalis; Wet Prep; Trichomonas culture; Trichomonas vaginalis RNA; Trichomonas vaginalis DNA probe
Formal name: Trichomoniasis
Related tests: Pap smear, Chlamydia, Gonorrhea

At a Glance

Why Get Tested?

To diagnose an infection with T. vaginalis, a microscopic, single cell (protozoan) parasite that is usually transmitted sexually, causing vaginal infections in women and urethritis and prostatitis in men

When to Get Tested?

When a woman shows symptoms of infection, such as a strong-smelling vaginal discharge, genital itching, and/or pain during urination, or if a man has the frequent urge to urinate and/or a discharge from the urethra

Sample Required?

In women, a swab of vaginal or cervical secretions; a sample may be obtained from the same thin-layer collection vial used for a Pap smear; in men, a urethral swab is required. Other sources may include urine or prostatic fluid.

Test Preparation Needed?

None

The Test Sample

What is being tested?

To diagnose 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 US Centers for Disease Control and Prevention, trichomoniasis is the most common, curable sexually transmitted disease (STD) in young, sexually active women. In this country, an estimated 7.4 million new cases occur each year in women and men, with the highest number of cases seen in women between the age of 16 and 35 years.

Trichomonas vaginalis is one of the most common causes of vaginitis in women. Symptoms include:

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

These symptoms may take several days to several weeks to develop; however, treatment is easy with prescription antibiotics. All current sexual activity should cease during treatment, and any partners should be treated at the same time to avoid re-infection.

A long-term, non-treated infection may cause tissue changes in the cervix of women, which can be detected during a Pap smear. Having trichomoniasis during pregnancy can cause complications and may contribute to premature birth or having a baby with low birth weight.

How is the sample collected for testing?

In women, a swab of secretions is collected from the vagina. In men, a swab is inserted into the urethra. Urine samples may also sometimes be used.

NOTE: If undergoing medical tests makes you or someone you care for anxious, embarrassed, or even difficult to manage, you might consider reading one or more of the following articles: Coping with Test Pain, Discomfort, and Anxiety, Tips on Blood Testing, Tips to Help Children through Their Medical Tests, and Tips to Help the Elderly through Their Medical Tests.

Another article, Follow That Sample, provides a glimpse at the collection and processing of a blood sample and throat culture.

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 Trichomonas vaginalis. In women, small red sores may be visible on the walls of the vagina or cervix during a pelvic exam. The secretions from the vagina or urethra that are collected on a swab can be examined under a microscope (called a wet prep), cultured, or tested with molecular assays to detect the presence of the parasite.

Examination of the wet prep determines whether the symptoms presented are caused by an infection with T. vaginalis through direct observation. It is placed under a microscope (phase-contrast microscope) to visually see the presence of the parasite. While this method is simple and quick, visualization of the parasite can be missed due to sampling error.

A more sensitive test is to culture the sample, but up to 7 days is required for the culture to grow adequately enough for identification of the parasite. Other methods that are available include direct fluorescent antibody (DFA) test and a test that detects trichomonas antigens.

Molecular testing using direct DNA probes or PCR (Polymerase Chain Reaction) technology offer the most sensitive and timely determination (usually within 24 hours). Samples can be obtained during a routine gynecologic examination that includes a Pap smear.

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When is it ordered?

Your doctor may order a test for T. vaginalis if you complain of symptoms, such as foul-smelling vaginal discharge or pain on urination. If you have an infection with another sexually transmitted disease, your doctor might test for trichomonas as well. Likewise, if results indicate that you are infected with trichomonas, you may also be tested for chlamydia and gonorrhea since these STDs often occur together.

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What does the test result mean?

A positive test indicates an active infection that requires treatment with a course of prescription medication.

If you are infected, your sexual partner(s) should also be tested and treated as well.

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Is there anything else I should know?

An infected person is at greater risk of getting other sexually transmitted diseases. In particular, the genital inflammation that occurs with trichomonas can increase a woman's susceptibility to HIV infection if exposed to the virus.

Neonatal trichomoniasis, though rare, can also 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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Common Questions

1.  How long does it take to get results?

If your doctor can see red sores on the vaginal wall, your doctor will most likely perform a wet prep and check it under a microscope for the parasite. There is also a rapid test that can detect trichomonas antigens in 10 minutes. However, other methods that require your sample to be sent to a laboratory may take longer to get results. A culture can take up to 7 days while molecular methods can produce a result in 24 hours. A method that involves a self-contained pouch system for the detection of T. vaginalis from female vaginal samples or male urethra/urine samples contains a medium that is unique for the transport and growth of T. vaginalis, while inhibiting the growth of contaminating microorganisms that might interfere with a reliable diagnosis. Results from this method may be available within 24 to 72 hours.

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2.  What other complications can occur if not properly treated?

Untreated or improperly treated trichomoniasis can result in an infection that can increase the risk of pelvic inflammatory disease (PID) in women. Men are sometime asymptomatic, resulting in chronic infection and re-infection of partner(s).

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3.  How can trichomoniasis be prevented?

The American Social Health Association has information on ways to reduce your risk.

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Article Sources

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NOTE: This article is based on research that utilizes the sources cited here as well as the collective experience of the Lab Tests Online Editorial Review Board. This article is periodically reviewed by the Editorial Board and may be updated as a result of the review. Any new sources cited will be added to the list and distinguished from the original sources used.

Sources Used in Current Review

Wu, A. (2006). Tietz Clinical Guide to Laboratory Tests, Fourth Edition. Saunders Elsevier, St. Louis, Missouri. Pp 1618.

Planned Parenthood: Trichomoniasis. Available online at http://www.plannedparenthood.org/health-topics/stds-hiv-safer-sex/trichomoniasis-4282.htm through http://www.plannedparenthood.org. Accessed June 2009.

Centers for Disease Control and Prevention. Fact Sheet: Trichomoniasis. Available online at http://www.cdc.gov/std/trichomonas/STDFact-Trichomoniasis.htm through http://www.cdc.gov. Accessed June 2009.

American Social Health Association: VAGINITIS/TRICHOMONIASIS. Available online at http://www.ashastd.org/learn/learn_vag_trich_tri.cfm through http://www.ashastd.org. Accessed June 2009.

MedlinePlus Medical Encylopedia: Trichomoniasis. Available online at http://www.nlm.nih.gov/medlineplus/ency/article/001331.htm. Accessed June 2009.

TeensHealth: Trichomoniasis. Available online at http://kidshealth.org/teen/infections/stds/std_trichomoniasis.html through http://kidshealth.org. Accessed June 2009.

Petrin D, Delgaty K, Bhatt R, et. al. Clinical and microbiological aspects of Trichomonas vaginalis. Clin Microbio Rev 11:300-317, 1998.

Briselden AM, Hiller SL. Evaluation of Afirm VP microbial identification for Gardnerella vaginalis and Trichomonas vaginalis. J Clin Microbiol 32:148-152, 1994.

DeMeo LR, Draper DL, McGregor JA, et. al. Evaluation of deoxyribonucleic acid probe for the detection of Trichomonas vaginalis in vaginal secretions. Am J Obstet Gynecol 174:1339-1342, 1996.

Rubino S, Muresu R, Rappelli P, et. al. Molecular probe for identification of Trichomonas vaginalis DNA. J Clin Microbiol 29:702-706, 1991.

Witkin SS, Inglis SR, Polaneczky M, et. al. Detection of Chlamydia trachomatis and Trichomonas vaginalis by polymerase chain reaction in introital specimens from pregnant women. Am J Obstet Gynecol 175:165-167, 1996.

Campbell L, Woods V, Lloyd T, Elsayed S, Church DL. Evaluation of the OSOM Trichomonas rapid test versus wet preparation examination for detection of Trichomonas vaginalis vaginitis in specimens from women with a low prevalence of infection. J Clin Microbiol 2008 Oct; 46(10):3467-9.

Sources Used in Previous Reviews

Centers for Disease Control and Prevention: Trichomonas Fact Sheet. Available online at http://www.cdc.gov/ncidod/dpd/parasites/trichomonas/factsht_trichomonas.htm through http://www.cdc.gov.

American Social Health Association: VAGINITIS/TRICHOMONIASIS, Questions & Answers. Available online at http://www.ashastd.org/learn/learn_vag_trich.cfm through http://www.ashastd.org.