Polymerase Chain Reaction (PCR)

Switch to mobile view »

Details of the first polymerase chain reaction (PCR) test for Trichomonas vaginalis were published in 1992.1 PCR quickly and repeatedly proved to be the most accurate diagnostic method for T. vaginalis detection in both females and males. The most recent studies are reporting sensitivities and specificities approaching 100%.2

Diagnosis in Women

PCR initially showed mixed results for the detection of trichomoniasis in women.

In a 1998 study, PCR was compared to culture and wet mount for the detection of T. vaginalis in vaginal swabs obtained from 350 women attending a health clinic on a military base. The sensitivities of PCR, culture, and wet mount were 97%, 70%, and 36%, respectively.4

Sensitivity of T. vaginalis Detection Methods in Women
Study PCR Culture Wet Mount
Madico (1998)4 97% 70% 36%
Wendel (2002)5 84% 78% 52%
Schirm (2007)2 100% 71%
Table 1

In an observational study of 337 women in 2002, the diagnostic sensitivity of PCR for the detection of T. vaginalis was 84%, vs. 78% for culture and 52% for wet mount.5

In 2007, Schirm et al. reported using real-time PCR to analyze specimens from 1,978 women and 98 men who were suspected of having trichomoniasis. The sensitivity of PCR was 100%, and the specificity was 99.9%. The positive and negative predictive values were 95% and 100%. By comparison, culture and microscopy had a combined sensitivity of 71%.2

Diagnosis in Men

In men, PCR represents a marked improvement over other diagnostics for the detection of T. vaginalis.

In a 2002 study of 300 males attending an STD clinic PCR detection of T. vaginalis was significantly more sensitive than culture for diagnosis in males, revealing a prevalence of infection more than three times that found by combined cultures. Combined urine and urethral cultures showed a trichomoniasis prevalence of 5%, and PCR (urine and urethral swab) showed a 17% prevalence.3

Sensitivity of T. vaginalis Detection Methods in Men
Study PCR Culture Wet Mount
Wendel (2003)7 94% 28% -
Hobbs (2006)6 98% 22.5% -
Schirm (2007)2 100% 71%
Table 2

Out of 355 men tested for trichomoniasis in a 2003 study, 47 met the criteria for T. vaginalis infection as defined by a positive culture or a positive PCR test. PCR detected 94% of positive cases, and culture detected only 28%.7

Hobbs (2006) found that PCR was 98% sensitive in detecting T. vaginalis in multiple specimens from 205 men with trichomoniasis. In the same study, culture was 22.5% sensitive.1

As previously mentioned, Schirm (2007) found the sensitivity and specificity of real-time PCR to be 100% and 99.9% in a study that included 98 men.2

  1. Riley DE, Roberts MC, Takayama T, Krieger JN. Development of a polymerase chain reaction-based diagnosis of Trichomonas vaginalis. J Clin Microbiol. 1992 Feb;30(2):465-72.
  2. Schirm J, Bos PA, Roozeboom-Roelfsema IK, Luijt DS, Möller LV. Trichomonas vaginalis detection using real-time TaqMan PCR. J Microbiol Methods. 2007 Feb;68(2):243-7. Epub 2006 Sep 26.
  3. Schwebke JR, Lawing LF. Improved detection by DNA amplification of Trichomonas vaginalis in males. J Clin Microbiol. 2002 Oct;40(10):3681-3.
  4. Madico G, Quinn TC, Rompalo A, McKee KT Jr, Gaydos CA. Diagnosis of Trichomonas vaginalis infection by PCR using vaginal swab samples. J Clin Microbiol. 1998 Nov;36(11):3205-10.
  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 Sep 1;35(5):576-80. Epub 2002 Aug 6.
  6. Hobbs MM, Lapple DM, Lawing LF, Schwebke JR, Cohen MS, Swygard H, Atashili J, Leone PA, Miller WC, Seña AC. Methods for detection of Trichomonas vaginalis in the male partners of infected women: implications for control of trichomoniasis. J Clin Microbiol. 2006 Nov;44(11):3994-9. Epub 2006 Sep 13.
  7. Wendel KA, Erbelding EJ, Gaydos CA, Rompalo AM. Use of urine polymerase chain reaction to define the prevalence and clinical presentation of Trichomonas vaginalis in men attending an STD clinic. Sex Transm Infect. 2003 Apr;79(2):151-3.