It would be impractical, and indeed unnecessary, to refer all women with an abnormal vaginal discharge to GU medicine. Many women self-diagnose "thrush" and approach their GP requesting a repeat prescription of antifungals without investigation or examination. This is not an ideal approach to management. Confirmatory vaginal swabs should be taken on at least some occasions and if this is considered "difficult," for whatever reasons, then a GU medicine referral is advisable. There is also some concern that the availability of topical anti-"thrush" treatments without prescription may considerably delay some women from seeking professional help.
There are a few other points worth considering when deciding whether to refer a patient to GU medicine.
(1) In addition to obtaining optimal specimens for culture, microscopy of vaginal, cervical, and urethral secretions is performed routinely in all GU medicine clinics which enables the clinician to make, in many cases, an immediate diagnosis. Microscopy is an invaluable method of assessing the general health of the vagina and cervix. For example, a woman with symptomatic discharge showing a predominance of lactobacilli on the vaginal Gram stain, a normal cervical Gram stain and negative vaginal and cervical cultures, is most likely to have a physiological discharge.
(2) The two commonest causes of vaginal discharge seen in general practice and amongst attenders at GU medicine are candidiasis and bacterial vaginosis, neither of which are sexually transmitted. Microscopy of vaginal secretions is essential to accurately diagnose bacterial vaginosis; high vaginal swab culture is of no use.
(3) There are a few key questions that may give a clue to the diagnosis:
- Irritation or soreness is suggestive of candidiasis.
- A malodorous discharge is suggestive of bacterial vaginosis.
- Intermenstrual bleeding or pelvic discomfort, a recent change of sexual partner, and the use of non-barrier contraception increase the likelihood of sexually transmitted infection.
(4) Which swabs to take. A Stuart's swab for microbiological culture is usually adequate to detect genital tract pathogens. It is important that the swab reaches the laboratory as soon as possible: Trichomonas vaginalis and the gonococcus are particularly delicate and may not survive an overnight delay before reaching specific culture media.
Keep genital specimens for T. vaginalis culture at room temperature and swabs for Neisseria gonorrhoeae culture in the refrigerator if there is likely to be a delay before reaching the laboratory.
If gonorrhea is considered a possible diagnosis, the patient should be referred to GU medicine so that the appropriate swabs may be taken (i.e. urethral, cervical, rectal, and pharyngeal but NOT vaginal), plated on to the appropriate culture media and incubated prior to transport to the laboratory.
Chlamydia trachomatis is usually diagnosed by NAAT or antigen detection methods, such as the EIA. Wipe the cervix clear of vaginal secretions before taking an endocervical sample (i.e. a sample from the columnar epithelium) and remember that cellular material rather than mucus is required for diagnosis, although this is less of an issue for NAAT.
A 1-2 day delay in transport should not adversely affect the results. It is worth emphasizing that even with a perfectly taken clinical specimen the currently available EIA tests for Chlamydia may yield false positive or false negative results. Many laboratories will routinely retest positive samples using a different detection method from the original test. A positive result on both tests is likely to indicate a true infection. The significance of equivocal results must be judged on clinical merit. As our microbiology colleagues inform us, no test is 100% sensitive, sometimes a difficult concept to get over to our patients.
Bacterial vaginosis cannot be diagnosed from a vaginal swab unless a Gram stain is prepared.
Guidelines for the management of vaginal discharge are summarized in Table 7.1.