Special Article
A meta-analysis of the Papanicolaou smear and wet mount for the diagnosis of vaginal trichomoniasis

Presented in part at the Southern Society of General Internal Medicine, New Orleans, Louisiana, February 18–20, 1999, and at the 22nd Annual Meeting of the Society of General Internal Medicine, San Francisco, California, April 29–May 1, 1999.
https://doi.org/10.1016/S0002-9343(99)00466-0Get rights and content

Abstract

purpose: To obtain reliable estimates of the sensitivity and specificity of the cervical Papanicolaou (Pap) smear and wet mount to diagnose vaginal trichomoniasis.

methods: Articles indexed in MEDLINE (1976–1998) about diagnostic tests for trichomoniasis and their listed references were retrieved. Thirty studies (9,501 patients) that used trichomonas culture as a gold standard were selected. Studies were defined as level I if they fulfilled at least two of the following three criteria: consecutive patients were evaluated prospectively, the decision to culture was not influenced by test results, and there was independent and blind comparison with culture. Studies were classified as level II if one criterion was fulfilled, and as level III otherwise.

results: The pooled sensitivity of the Pap smear for the diagnosis of trichomoniasis among level I studies was 57% (95% confidence interval [CI]: 51% to 63%) and the pooled specificity was 97% (95% CI: 93% to 100%). The likelihood ratio for a positive Pap smear was 19 among level I studies (range: 8 to 62). The pooled sensitivity of the wet mount among level I studies was 58% (95% CI: 51% to 66%); among level II studies, the sensitivity was 72% (95% CI: 62% to 81%), and among level III studies, the sensitivity was 82% (95% CI: 67% to 97%). The overall specificity of the wet mount was 99.8%.

conclusions: A positive Pap smear for trichomonads in settings in which trichomoniasis is common (prevalence ≥20%) requires treatment. A positive Pap smear is indeterminate when the prevalence of trichomoniasis is about 10%; thus, clinicians should either confirm the diagnosis by culture or treat all such patients, recognizing that some patients will be treated unnecessarily. A culture should be obtained in women with a positive Pap smear who are unlikely to have trichomoniasis (prevalence ≤1%). While a positive wet mount is diagnostic, a negative wet mount does not exclude trichomoniasis.

Section snippets

Identification of studies

We searched the MEDLINE database in all languages for articles published between January 1976 and February 1998 that described diagnostic tests for vaginal trichomoniasis in women (Ovid 7.05, Ovid, Technologies Inc., New York, New York). The keywords to identify trichomoniasis were explode (exp) trichomonas, exp trichomonas infections, trichomonas vaginalis, and trichomonas vaginitis. Terms under each subheading were also retrieved. The text word trichomonas and the wild card trichomon$ were

Results

We classified 12 (39%) studies as level I, 15 (48%) as level II, and 4 (13%) as level III (Table 1). The study design included a prospective evaluation of consecutive patients in 11 (35%) investigations. The test results did not influence the decision to perform trichomonas culture as a gold standard in 27 (87%) studies, and the test and culture were examined independently and blindly in 4 (13%) studies. An appropriate spectrum of patients was included in 16 (52%) of the reports, and the study

Discussion

Effective control of trichomoniasis will require a coordinated effort by clinicians and public health authorities to institute prevention and treatment programs. The success of this effort depends in part on the availability of a rapid, convenient, and accurate test to make the diagnosis in women with symptomatic vaginitis, and to screen for the infection in populations with a high prevalence of infection. The 1998 guidelines of the Centers for Disease Control and Prevention for the treatment

Acknowledgements

We thank Amy Jackson and Laurin Gibson for technical assistance, and Drs. Diana Antonacci, James Byrd, and Harry Adams for reviewing the paper.

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