Question
What are the procedures for testing and the results of the tests performed on high vaginal swabs analyzed in three laboratories in London?
Design
The standard procedures for analyzing high vaginal swabs and the results of testing were compared for three laboratories in London.
Participants
Seven hundred ninety-seven high vaginal swabs (HVS) received at 3 diagnostic microbiology laboratories from general practices in London during a 4-week period were tested. Seventy-nine percent of the HVS were from women age 25 or older (median = 31, range = 15-95), 72% presented with symptoms suggestive of a lower genital tract infection.
Description of Tests and Diagnostic Standard
The standard testing procedures and the test results for HVS sent to the 3 diagnostic microbiology laboratories were determined.
Main Results
The standard test procedures for HVS at each laboratory are shown in Table 1. The diagnoses obtained from HVS by laboratory are shown in Table 2. All but one C. trachomatis positive specimen were from woman less than 25 years old.
Table 1. Testing procedures for high vaginal swab specimens at 3 diagnostic microbiology laboratories in London
|
Procedure
|
Laboratory A
|
Laboratory B
|
Laboratory C
|
|
Sabouraud agar culture for Candida spp.
|
Yes
|
Yes
|
Yes
|
|
T. vaginalis culture
|
No
|
Yes
|
Yes
|
|
Wet mount for T. vaginalis and clue cells
|
Yes
|
No
|
No
|
|
Gram stain
|
To confirm clue cells on wet mount
|
No
|
Only if “discharge” indicated
|
|
Culture for N. gonorrhoeae
|
Only if no endocervical swab
|
Only if requested
|
Yes
|
|
Full aerobic and anaerobic culture
|
Only if pregnant or history suggestive of upper tract infection
|
Only aerobic on blood agar
|
Yes
|
|
C. trachomatis assay
|
LCR
|
EIA
|
EIA
|
Table 2. Diagnoses obtained from high vaginal swabs by 3 diagnostic microbiology laboratories in London
|
Diagnosis
|
Number with diagnosis/number tested
|
|
Laboratory A
|
Laboratory B
|
Laboratory C
|
|
Candida spp.
|
35/150
|
43/218
|
97/427
|
|
Clue cells
|
15/150
|
Not done
|
11/300
|
|
T. vaginalis
|
0/150
|
1/218
|
4/427
|
|
N. gonorrhoeae
|
0/76
|
Not done
|
1/425
|
|
C. trachomatis
|
4/99
|
1/93
|
4/131
|
Authors’ Conclusions
There was considerable variation among the three laboratories in the processing of high vaginal swab specimens. Other than Candida spp., the diagnostic yield of other pathogens was low. The usefulness of HVS for the diagnosis and management of vulvovaginal symptoms in general practice remains unclear.
Source of funding: None given.
For correspondence: Eva Jungmann, Archway Sexual Health Clinic, Whittington Hospital, Highgate Hill, London N19 5NF, UK. E-mail address: eva.jungmann@camdenpct.nhs.uk.
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