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The specificity of a G.
vaginalis DNA hybridization test compared well with a Gram stain
scoring system for the diagnosis of bacterial vaginosis in pregnant women.
DNA hybridization
test: rapid diagnostic tool for excluding bacterial vaginosis in
pregnant women with symptoms suggestive of infection.
Witt A, Petricevic L,
Kaufmann U, Gregor H, Kiss H.
Journal of Clinical
Microbiology 2002;40:3057-3059.
Summary:
Question
Can a DNA hybridization test be used as an alternative to Gram-stained
microscopic slides for diagnosis of bacterial vaginosis?
Design
This study describes a prospective comparison of a DNA hybridization test
with Gram stain for the diagnosis of bacterial vaginosis (BV) in pregnant
women.
Participants
One thousand seven hundred twenty-five women between the 12th and 36th
weeks of gestation attending the outpatient clinic of the Department of
Obstetrics and Gynecology at the University of Vienna, who presented with
clinical symptoms of increased vaginal discharge combined with pruritus
and/or burning, cervical incompetence, lower abdominal pain, preterm
labor, or preterm rupture of the membranes were included in the study.
Description of Tests and Diagnostic
Standard
Separate vaginal samples collected on Dacron swabs were tested by the
Affirm VPIII G. vaginalis DNA hybridization assay (Becton Dickinson,
Sparks, MD), according to the manufacturer's protocol, and by the
evaluation of a Gram-stained microscopic slide according to the Nugent
scoring system, modified to classify into four categories. Grade 0
corresponded to a smear with no microbes, grade 1 to a Nugent score <4,
grade 2 to a Nugent score of 4 to 6, and grade 3 to a Nugent score >6.
Grade 3 showed the flora typical of bacterial vaginosis.
Main Outcome Measures
The sensitivity, specificity, positive predictive value (PPV), and
negative predictive value (NPV) for the DNA hybridization test compared to
the Gram stained slide evaluated by a modified Nugent scoring system for
the diagnosis of bacterial vaginosis were determined.
Main Results
The results of the Gram stain, presented by grade, versus the
hybridization test are shown in the table. When grade 2 cases were
included with grade 3 as positive for bacterial vaginosis, the
sensitivity, specificity, PPV, and NPV of the DNA hybridization test were
73.2%, 97.1%, 88.7%, and 92.2%, respectively. When grade 2 cases were
subtracted from the analysis, and grade 3 cases only were considered
positive for BV, the sensitivity, specificity, PPV, and NPV of the DNA
hybridization test were 89.5%, 97.1%, 80.1%, and 98.6%, respectively.
However, if grade 2 cases are included with grades 0 and 1 as negative for
bacterial vaginosis, the sensitivity, specificity, PPV, and NPV of the DNA
hybridization test are 89.5%, 88.3%, 45.7%, and 98.7%, respectively.
| Gram stain versus
hybridization test in the detection of bacterial vaginosis |
| Gram
stain |
Hybridization
test |
|
Grade |
Number of
smears |
Negative |
Positive |
| 0 and 1 |
1319 |
1281 |
38 |
| 2 |
235 |
91 |
144 |
| 3 |
171 |
18 |
153 |
| Total |
1725 |
1390 |
335 |
Authors' Conclusions
The DNA hybridization test can be used as a
rapid diagnostic tool to exclude bacterial vaginosis in pregnant women
with symptoms.
Source of funding: None given.
For correspondence: Herbert Kiss,
Department of Obstetrics and Gynecology, University of Vienna Medical
School, Wahringer Gurtel 18-20, A-1090 Vienna, Austria. E-mail address: herbert.kiss@akh-wien.ac.at.
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