Trichomoniasis often goes undiagnosed. The most commonly used diagnostic test is at best 60-70% sensitive, according to the CDC.1
For both women and men, a health care provider must perform a physical examination and laboratory test to diagnose trichomoniasis.
To diagnose trichomoniasis in a woman, her health care provider will first look at her vagina and vaginal discarge. Normal discharge is usually clear, but in trichomoniasis it may appear yellow or greenish in color. The discharge may be tested for abnormal or foul odor using a potassium hydroxide (KOH) "whiff test," and its acidity may be checked.
If trichomoniasis is suspected, further tests will be conducted. Diagnostic methods range from simple visual detection under a microscope to polymerase chain reaction (DNA analysis.) Each method has its advantages, but no single method is ideal.
Wet Mount
For a wet mount, a microscope slide is prepared by suspending a specimen in saline solution. The slide is then visually examined for trichomonads. Wet mount is the most common method used to diagnose trichomoniasis. It is at best 60% sensitive, however, and is best used as a screening tool.
Culture / InPouch™ TV (BioMed Diagnostics)
For this method, a specimen is placed in a culture medium for 2-7 days before it is examined. If trichomonads are present in the original specimen, they will multiply while in culture and be easier to detect. Culture is considered the gold standard for the diagnosis of trichomoniasis. It is both highly sensitive and highly specific. Its disadvantages include cost and prolonged time before diagnosis.
BioMed Diagnostics' InPouch TV system is a two-chambered bag that allows one to perform a wet mount using the upper chamber and a culture using the lower chamber. The wet mount's fast results allow some patients to begin treatment without having to wait, untreated, for the results of the more sensitive culture.
Affirm™ VPIII Microbial Identification Test (BD)
BD's Affirm VPIII Test is a moderately complex DNA probe for vaginitis. Identification of Candida (yeast) species, Gardnerella vaginalis, and Trichomonas vaginalis is possible from a single vaginal sample. The test's sensitivity for detecting T. vaginalis is high, and it can provide results in as little as 45 minutes.
OSOM® Trichomonas Rapid Test (Genzyme Diagnostics)
Genzyme Diagnostics' OSOM Trichomonas Rapid Test is a new point-of-care, antigen-detecting diagnostic test for trichomoniasis. By inserting a vaginal swab into a test tube with 0.5 mL of a special buffer, mixing the solution vigorously by hand, removing the swab, and then inserting a test strip, physicians and staff can read results in 10 minutes. The OSOM test is more sensitive than wet mount.
Polymerase Chain Reaction
In polymerase chain reaction (PCR), sample is treated with enzymes that amplify specific regions of T. vaginalis' DNA. After amplification, the number of DNA fragments are quantified. PCR has proven to be the most accurate diagnostic method in recent studies. PCR is currently only used in research, not clinical settings.
Other Tests
Potassium Hydroxide (KOH) "Whiff Test"
The "whiff" test is a rudimentary technique that may be used as part of a clinical diagnosis. The test is conducted by mixing a swab of vaginal fluid with a 10% potassium hydroxide solution, then smelling it. A strong amine (fishy) smell could be an indication of trichomoniasis or bacterial vaginosis.
Vaginal pH Test
Trichomonads grow best in less acidic environments, and elevated vaginal pH may be an indication of trichomoniasis. A healthcare provider performs the test by touching pH paper to the vaginal wall or to a vaginal swab specimen, then comparing it to color scale to determine the pH.
Papanicolaou Test (Pap Smear)
The Papanicolaou test is a microscopic examination of a stained specimen. It is mainly used as a diagnostic test for the screening of various cervical abnormalities and genital infections. While it may occasionally detect trichomonads, it has a high diagnostic error rate and is not suitable for screening unless used in conjunction with a more sensitive test.
