Examination and testing of the genital area
Specimens for sexually transmitted infection tests are taken during examination of the genital tract. In order to optimize the quality of the samples, it is suggested that the tests are taken according to the manufacturer’s instructions and in the sequence set out below.
Inspect the vulval, pubic and peri-anal areas first, then pass a speculum into the vagina. If there are lesions at the introitus that would make this painful, such as herpetic ulcers, consideration should be given to deferring further examination. A high vaginal swab for Trichomonas vaginalis, candidiasis and bacterial vaginosis is taken from the vaginal walls and posterior fornix and used to test for pH and sent for microscopy, culture and sensitivity (MC&S) analysis. If indicated, a cervical smear should be taken for cytology at this stage. The ectocervix should then be wiped to remove any vaginal discharge. An endocervical swab, to be sent for MC&S analysis, is then taken for gonorrhea testing. An endocervical or urinary chlamydia test should also be taken, depending on which test is offered by the local laboratory. If a cervical test is to be taken for chlamydia it is important to sample endocervical cells (as chlamydia is an intracellular organism) by rotating the swab against the wall of the endocervix (Table Basic testing for sexually transmitted infections (triple swabs)). The diagnosis of chlamydia and gonorrhea can be improved if urethral swabs are taken in addition to cervical samples. Urethral tests require samples to be taken with a narrow swab or loop and can be uncomfortable and are unacceptable to many women. Testing the rectum and pharynx for gonorrhea should be considered if the partner has urethral gonorrhea and anal or oral (fellatio) intercourse has occurred. A bimanual pelvic examination should be performed to detect signs of pelvic inflammatory disease (pelvic inflammatory disease), uterine or ovarian pathology. This is especially important if gonorrhea or chlamydia is suspected or there is a history of pelvic or low abdominal pain or dyspareunia. A general physical examination including the mouth and skin may reveal signs of parasitic infection, syphilis, HIV and complications of sexually transmitted infections. Testing for other sexually transmissible infections such as syphilis, HIV, hepatitis B and C should be considered.
Table Basic testing for sexually transmitted infections (triple swabs)
|Organism/condition tested for||Test performed|
|High vaginal swab|
|Candida and trichomonas||Microscopy, culture and sensitivity|
|bacterial vaginosis||Microscopy as above|
|Gonorrhea||Mcroscopy, culture and sensitivity|
|Endocervical swab or urine *|
|Chlamydia||Use most sensitive test available locally, these may include: EIA, LCR, PCR, DIF, culture|
|bacterial vaginosis and trichomonas||pH, using narrow range pH paper|
|bacterial vaginosis||Amine test|
*Depends on test used; EIA, enzyme immunoassay; LCR, ligase chain reaction; PCR, polymerase chain reaction; DIF, direct immunofluorescence; bacterial vaginosis, bacterial vaginosis
pH and amine testing
In community settings a preliminary assessment of vaginal discharge may be made by noting the character of the discharge, the presence of inflammation and by testing the pH; some also advocate amine testing (Table Features helpful in the preliminary assessment of vaginal discharge). Vaginal discharge may not be typical and these tests are not sufficiently specific to provide a definitive diagnosis but may be useful especially where microscopy is not available. A sample of vaginal secretion should be placed on pH paper such as Whatmans narrow range pH paper. Care should be taken to avoid sampling cervical mucus or lubricant placed on the speculum, which would artificially raise the pH. pH testing is also unreliable in the presence of semen, menstrual fluid, vaginal treatments such as spermicides, douches and some systemic drugs. The pH is normal (< 4.5) in candidiasis but > 4.5 in bacterial vaginosis and trichomoniasis.
Table Features helpful in the preliminary assessment of vaginal discharge
|Organism/ condition||Classic description of discharge||Inflammation of vagina||PH||Amine test|
|Bacterial vaginosis||Grey, thin, homogenous||Absent||>4.5||Positive|
|Trichomonas vaginalis||Yellow/green, thin, frothy||Present||>4.5||Positive|
|Candida Spp.||White, curdy||Present||<4.5||Negative|
The amine test is performed by adding a drop of 10% potassium hydroxide to a sample of vaginal discharge on a glass slide. Amines are released which can be detected by their characteristic odor. The amine test is positive in bacterial vaginosis or trichomoniasis (because of the accompanying overgrowth of anaerobes) and weakly positive with menstrual blood or semen. Potassium hydroxide is corrosive and should be handled and stored with care.
Transport and storage of specimens
If specimens cannot be plated for culture at the time of collection, appropriate transport media should be used. A charcoal-based medium, for example, is often recommended for gonorrhea culture. High vaginal and endocervical swabs for bacterial culture should be kept at room temperature. Urine specimens for bacterial culture and swabs for viral and chlamydia culture usually require refrigeration and the temperature needs to be maintained until the specimen reaches the laboratory. Individual practices should check the manufacturer’s instructions and seek advice from their local laboratory. If a significant delay in the transport of cultures to the laboratory is likely for a patient with suspected gonorrhea, immediate referral to a genitourinary medicine clinic should be considered.