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A simplified
grading scheme for Gram stained smears can be used as an alternative
to Amsel's criteria for the diagnosis of bacterial vaginosis.
Validation of a
simplified grading of Gram stained vaginal smears for use in
genitourinary medicine clinics.
Ison CA, Hay PE.
Sex Transm Infect. 2002;78:413-415.
Summary:
Question
How well does a method using a simplified grading scheme for Gram stained
smears of vaginal fluid compare to the Amsel composite criteria for the
diagnosis of bacterial vaginosis?
Design
Gram stained vaginal fluid smears were assessed qualitatively according to
a specific protocol. The grade of the slide was compared to a diagnosis of
bacterial vaginosis (BV) made according to the Amsel criteria.
Participants
One hundred sixty two smears from 72 women who were part of an
investigator blind, randomized, parallel group, multicenter, phase IV
treatment study comparing metronidazole gel and clindamycin cream were
evaluated.
Description of Tests and Diagnostic
Standard
During a vaginal examination, a smear of vaginal fluid collected from the
lateral fornix was prepared by the clinician. All smears were sent to a
central laboratory where they were Gram stained and examined by a single
reader under oil immersion at 1000X magnification. Smears were graded as
follows: grade 0, epithelial cells with no bacteria seen; grade I (normal
flora), lactobacillus morphotype only; grade II (intermediate flora),
reduced lactobacillus morphotype with mixed bacterial morphotypes; grade
III (BV), mixed bacterial morphotypes with few or absent lactobacillus
morphotypes; and grade IV, epithelial cells covered with Gram positive
cocci only. After the initial analysis, all discrepant slides were reread
(blinded to the original result) and gave identical results. BV was
diagnosed using Amsel criteria.
Main Outcome Measures
The sensitivity, specificity, positive predictive value (PPV), and
negative predictive value (NPV) of the Gram stain score for the diagnosis
of BV as determined using Amsel criteria were calculated.
Main Results
BV was diagnosed in 83/162 (51%) patient visits. The majority of patient
visits without BV had smears assessed as grade I (48/79, 61%), and those
with BV had smears assessed as grade III (80/83, 96%). Grade II was found
among 12/79 (15%) patient visits without BV and 1/83 (1%) with BV. Six
smears graded as 0, and 8 smears graded as IV were found only among normal
patient visits. The performance of grading Gram stained smears for the
diagnosis of BV using Amsel criteria is shown in the table.
| Performance
values of grading Gram stained vaginal smears for the diagnosis of
BV as defined by Amsel criteria |
|
Grading criteria |
Performance
parameter |
|
Sensitivity |
Specificity |
PPV |
NPV |
Grade I = negative
Grade II excluded
Grade III = positive |
97.5 |
90.5 |
94.1 |
96.0 |
Grades I, II = negative
Grade III = positive |
96.0 |
90.5 |
94.1 |
96.0 |
Grade I = negative
Grades II, III = positive |
97.5 |
73.8 |
82.6 |
96.0 |
Authors' Conclusions
There was a strong association of grade I
flora with normal women and of grade III with BV with resulting high
sensitivity, specificity, and predictive values which were similar or
higher than other grading schemes compared to the composite criteria.
These results indicate that when there is a lack of time or expertise,
this qualitative assessment of the microbial flora can be used as an
alternative method of diagnosis.
Source of funding: 3M Health Care Ltd.
For correspondence: C. A. Ison,
Medical Microbiology, Faculty of Medicine, Imperial College, St. Mary's
Campus, Norfolk Place, London W2 1PG, UK. E-mail address: c.ison@ic.ac.uk.
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