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The efficiency of
detecting gonorrhea by microscopy varies depending on the serovar
and auxotype of the infecting strain.
Sensitivity of
microscopy for the rapid diagnosis of gonorrhoea in men and women and the
role of gonorrhoea serovars.
Manavi K, Young H, Clutterbuck D
International
Journal of STD & AIDS 2003;14:390-394
Summary:
Question
What is the sensitivity of the microscopic diagnosis of genital gonorrhea
by N. gonorrhoeae serovar in males and females attending a
genitourinary medicine clinic?
Design
This study describes a retrospective examination of the Gram stain result
and the N. gonorrhoeae auxotype and serovar among cases of positive
culture for N. gonorrhoeae at a genitourinary medicine clinic.
Participants
Five hundred ninety-six cases of positive culture for N. gonorrhoeae
occurring at the Genitourinary Medicine clinic of the Royal Infirmary of
Edinburgh from 1995 to 1999, including the auxotype and serovar of each
isolate, were evaluated.
Description of Tests and Diagnostic
Standard
Gram staining and microscopy of urethral samples from men and of urethral
and cervical samples from women were performed on patients who were
symptomatic, who were contacts of partners with gonorrhea, or who had
signs of infection on examination. Microscopy was performed by doctors on
samples from men, and by a Medical Laboratory Scientific Officer on those
from women. Samples from the urethra of all patients, from the cervix of
female patients, from the rectum of women and men who have sex with men (MSM),
and from the pharynx of those with microscopically observed Gram-negative
intracellular diplococci at another site, of contacts of partners with
gonorrhea, and of all MSM and female sex workers were plated onto modified
New York City agar for culture of N. gonorrhoeae.
Main Outcome Measures
The prevalence of gonorrhea and the sensitivity of microscopy for
detecting infection were compared by patient group and by N.
gonorrhoeae auxotype and serovar.
Main Results
Two hundred ninety-seven (49%), 107 (18%), and 192 (32%) of 596 N.
gonorrhoeae culture positive cases were MSM, women, and heterosexual
men, respectively. The sensitivities of gonorrhea diagnosis by microscopic
examination of samples from anogenital sites for these three patient
groups are shown in the table. Serovars1B31 and 1B02 were frequently
undetected by microscopy in samples from females and MSM, respectively,
while serovar 1A02 was more likely to be missed by microscopy in samples
from heterosexual men. Negative microscopy was more probable with auxotype
NR in samples from MSM and females (P=0.0002) and with auxotype AHU
among heterosexual males (P=0.0005).
Authors' Conclusions
The sensitivity of microscopy in the rapid
diagnosis of gonorrhea was highest for urethral infection among MSM.
Infections with certain N. gonorrhoeae serovars were less likely to
be detected by microscopy.
Source of funding: None given.
For correspondence:
Kaveh Manavi, Department of Genitourinary Medicine, Royal Infirmary of
Edinburgh, Lauristan Place, Edinburgh EH3 9YW, UK. E-mail address: tirbad@yahoo.com
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