Trichomonas vaginalis by Nucleic Acid Amplification
Clinical Information Discusses physiology, pathophysiology, and general clinical aspects, as they relate to a laboratory test
Trichomonas vaginalis (TV) is a protozoan parasite that commonly infects the genital tract of men and women. It is now considered to be the most common curable sexually transmitted disease (STD) agent, with an estimated 3.7 million infected individuals in the United States.(1-4) Although up to 70% of infected individuals are asymptomatic, infections may be associated with vaginitis, urethritis, and cervicitis in women, and urethritis and prostatitis in men.(3) Patients that are infected with Trichomonas vaginalis have an increased risk of acquiring other sexually transmitted infections such as HIV, while infections in pregnant women are associated with premature labor, low-birth-weight offspring, premature rupture of membranes, and post-hysterectomy/post-abortion infection.(3)
Symptoms of Trichomonas vaginalis overlap considerably with other sexually transmitted infections, and therefore laboratory diagnosis is required for definitive diagnosis. The most commonly used method for detection is microscopic examination of a wet-mount preparation of vaginal secretions. However, this method has only 35% to 80% sensitivity compared with culture.(5) Culture also suffers from relatively low sensitivity (38%-82%) when compared to molecular methods.(5) Culture is also technically challenging and takes 5 to 7 days to complete. Molecular methods, such as the APTIMA Trichomonas vaginalis Assay, offer the highest sensitivity and specificity for detection of trichomoniasis. The APTIMA test utilizes target capture, transcription-mediated amplification (TMA), and hybridization protection assay (HPA) technologies for detection of Trichomonas vaginalis ribosomal RNA (rRNA).
A positive result is considered indicative of current or recent Trichomonas vaginalis infection (trichomoniasis).
Cautions Discusses conditions that may cause diagnostic confusion, including improper specimen collection and handling, inappropriate test selection, and interfering substances
The effects of tampon use, douching, and specimen collection variables have not been assessed for their impact on the detection of Trichomonas vaginalis.
To ensure proper endocervical sampling, excess mucus should first be removed.
Urine, vaginal swab, and PreservCyt Solution liquid Pap specimen sampling is not designed to replace cervical exams and endocervical specimens for diagnosis of female urogenital infections. Patients may have cervicitis, urethritis, urinary tract infections, or vaginal infections due to other causes or concurrent infections with other agents.
This assay has only been approved by the FDA for the specimen types indicated. Performance with other specimen types has not been evaluated by the manufacturer.
Reliable results are dependent on adequate specimen collection. Because the transport system used for this assay does not permit microscopic assessment of specimen adequacy, training of clinicians in proper specimen collection techniques is necessary.
Therapeutic failure or success cannot be determined with the APTIMA Trichomonas vaginalis assay since nucleic acid may persist following appropriate antimicrobial therapy.
Results from the APTIMA Trichomonas vaginalis assay should be interpreted in conjunction with other clinical data and symptoms.
A negative result does not preclude a possible infection because results are dependent on adequate specimen collection. Test results may be affected by improper specimen collection, preanalytical errors, technical errors, or target levels below the assay limit of detection. Furthermore, a negative result does not preclude a possible infection because the presence of Trichomonas tenax or Pentatrichomonas hominis in a specimen may affect the ability to detect Trichomonas vaginalis rRNA.
Assay performance of the APTIMA Trichomonas vaginalis assay has not been evaluated in the presence of Dientamoeba fragilis.
The APTIMA Trichomonas vaginalis assay has not been validated for use with vaginal swab specimens collected by patients.
Performance of the vaginal swab specimen has not been evaluated in pregnant women or in women <14 years of age.
Reference Values Describes reference intervals and additional information for interpretation of test results. May include intervals based on age and sex when appropriate. Intervals are Mayo-derived, unless otherwise designated. If an interpretive report is provided, the reference value field will state this.
Clinical References Provides recommendations for further in-depth reading of a clinical nature
1. Weinstock H, Berman S, Cates W Jr: Sexually transmitted diseases among American youth: incidence and prevalence estimates, 2000. Perspect Sex Reprod Health 2004;36(1):6-10
2. Soper D: Trichomoniasis: under control or undercontrolled? Am J Obstet Gynecol 2004;190(1):281-290
3. Centers for Disease Control and Prevention (CDC) Trichomoniasis-CDC Fact Sheet. Available from URL: http://www.cdc.gov/std/trichomonas/stdfact-trichomoniasis.htm Accessed August 2012
4. Schwebke JR, Burgess D: Trichomoniasis. Clin Microbiol Rev 2004;17(4):794-803
5. Wendel KA, Erbelding EJ, Gaydos CA, Rompalo AM: Trichomonas vaginalis polymerase chain reaction compared with standard diagnostic and therapeutic protocols for detection and treatment of vaginal trichomoniasis. Clin Infect Dis 2002;35(5):576-580