Papanicolaou Test (Pap Smear)

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Papanicolaou staining is mainly used as a diagnostic test for the screening of various cervical abnormalities and genital infections. The Pap test may reveal trichomonads, but the sensitivity and specificity of this method are low. Recent studies have reported sensitivities roughly ranging from 25% to 60% and have concluded that the Pap test is inadequate for trichomoniasis screening.1-6

Evaluation of PCR, Culture, Wet Mount, and Pap Test for the Diagnosis of Trichomoniasis1

Comparison of the diagnostic accuracy of the Pap test to the wet mount, culture, and PCR tests for the diagnosis of trichomoniasis. The Pap test showed 60.7 percent sensitivity, compared to 65.5 percent for wet mount, 78.7 percent for culture, and 100 percent for PCR.

A 2003 study comparing the diagnostic accuracy of the Pap test to polymerase chain reaction (PCR) found that approximately 40% of the population tested with the Pap test was misdiagnosed. The Pap test was 60.7% sensitive, compared to 65.6%, 78.7%, and 100%, for wet mount, culture, and PCR, respectively.1

In 2000, Wiese et al. published a meta-analysis of trichomoniasis diagnostic studies from 1976 and 1998. Pooled data from 30 studies, totaling 9,501 patients, showed the Pap test to be 57% sensitive.2

One advantage of the Pap smear for diagnosing trichomoniasis is that permanent samples can be stored and viewed later.3

  1. Lobo TT, Feijó G, Carvalho SE, Costa PL, Chagas C, Xavier J, Simoes-Barbosa A. A comparative evaluation of the Papanicolaou test for the diagnosis of trichomoniasis. Sex Transm Dis. 2003 Sep;30(9):694-9.
  2. Wiese W, Patel SR, Patel SC, Ohl CA, Estrada CA. A meta-analysis of the Papanicolaou smear and wet mount for the diagnosis of vaginal trichomoniasis. Am J Med. 2000 Mar;108(4):301-8.
  3. Lossick JG, Kent HL. Trichomoniasis: trends in diagnosis and management. Am J Obstet Gynecol. 1991 Oct;165(4 Pt 2):1217-22.
  4. Audisio T, Pigini T, de Riutort SV, Schindler L, Ozan M, Tocalli C, Bertolotto P. Validity of the Papanicolaou smear in the diagnosis of candida spp., Trichomonas vaginalis, and bacterial baginosis. J Low Genit Tract Dis. 2001 Oct;5(4):223-225.
  5. Ohlemeyer CL, Hornberger LL, Lynch DA, Swierkosz EM. Diagnosis of Trichomonas vaginalis in adolescent females: InPouch TV culture versus wet-mount microscopy. J Adolesc Health. 1998 Mar;22(3):205-8.
  6. 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.
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