Question
How well do clinical diagnoses based on combinations of symptoms and office-based testing compare with laboratory diagnoses of STI in women with lower genital tract signs and symptoms?
Design
Clinical diagnoses of STI in women with lower genital tract complaints were made using symptoms, signs, microscopy, and vaginal pH and amines and compared to the diagnoses made using laboratory testing for N. gonorrhoeae, T. vaginalis, C. trachomatis, yeast, and bacterial vaginosis in a prospective study.
Participants
Five hundred ninety-eight nonpregnant women from 3 sites, between 18 and 45 years old, who had one or more genital complaints including the presence of abnormal vaginal discharge (64%), a change in discharge (53%), abnormal vaginal odor (48%), vaginal itching (32%), lower genital tract burning (18%), and dysuria (12%), were tested. Sixty percent were black and 32% were white, 93.8% had a history of one or more previous genital tract infections.
Description of Tests and Diagnostic Standard
During a speculum examination, each woman was evaluated for mucopurulent cervicitis (yellow mucus on endocervical swab), vaginal secretions (color, viscosity, homogeneity), and odor before and after addition of potassium hydroxide. Vaginal specimens were collected for saline and KOH wet mounts, pH test, Gram stain, T. vaginalis culture on Diamonds media, and yeast culture on Sabouraud’s agar. Endocervical swabs were collected for Gram stain, N. gonorrhoeae culture on modified Thayer-Martin media, and C. trachomatis PCR assay.
Clinical diagnoses were based on symptoms, observations, and the results of several office-based tests. Yeast were diagnosed by buds or hyphae on wet mounts or KOH preparations, T. vaginalis was diagnosed by motile trichomonads on wet mounts, and bacterial vaginosis (BV) was diagnosed by Amsel criteria. Laboratory diagnoses were based on N. gonorrhoeae, T. vaginalis, and yeast cultures, C. trachomatis PCR, and evaluation of Gram stains by Nugent’s criteria for BV.
Main Outcome Measures
The sensitivity, specificity, and positive predictive value (PPV) of a clinical diagnosis of a lower genital tract infection were calculated compared to the laboratory diagnosis.
Main Results
The prevalence by laboratory diagnosis of BV, yeast, T. vaginalis, and C. trachomatis and/or N. gonorrhoeae in 598 women with lower genital complaints were 46%, 29%, 12%, and 11%, respectively. No infections were detected in 21%. The sensitivity, specificity, and PPV of each clinical diagnosis compared to the laboratory diagnosis are shown in the table.
Performance of clinical diagnosis of STI compared to laboratory diagnosis among 598 women with lower genital tract complaints
|
STI
|
Laboratory diagnosis method
|
Clinical diagnosis method
|
Performance of clinical diagnosis compared to laboratory diagnosis (%)
|
|
Sensitivity
|
Specificity
|
PPV
|
|
BV
|
Nugent Gram stain
|
Amsel criteria
|
92
|
77
|
80
|
|
yeast
|
Culture
|
Itching, wet mount
|
22
|
97
|
79
|
|
T. vaginalis
|
Culture
|
Wet mount
|
62
|
97
|
75
|
|
N. gonorrhoeae or C. trachomatis
|
Culture for N. gonorrhoeae, PCR for C. trachomatis
|
Endocervical mucopus
|
30
|
84
|
17
|
Authors’ Conclusions
The presumptive diagnosis of lower genital tract infections in women with genital tract complaints led to significant numbers of women being misdiagnosed or under diagnosed. Diagnosis and treatment that is based on symptoms is highly inaccurate and should be abandoned where resources permit.
Source of funding: Department of Defense grant.
For correspondence: Daniel V. Landers, Department of Obstetrics, Gynecology and Women’s Health, University of Minnesota, MMC 395, 420 Delaware St. SE, Minneapolis, MN 55455. E-mail address:
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