B. Endocervical swab – Explanation
The likely diagnosis here is cervicitis caused by either chlamydia or Neisseria
gonorrhoeae. The endocervix is the principal site to be tested. Swabs of the
endocervix can betaken during a speculum examination or indirectly by a vulvovaginal
swab. These samples are suitable to be sent for nucleic acid amplification test (NAATs),
cultures or microscopy.
A high vaginal swab (HVS) is only worthwhile where there are recurrent
symptoms,treatment failure or in pregnancy, postpartum, post-abortion or postinstrumentation.
Cervical cytology is a useful tool to screen for cervical cancers however it is a screening
tool for asymptomatic patients. There is no role for cervical smears for symptomatic
patients. Furthermore, cervical screening in the UK starts at age 25. Cervical cancer is
extremely rare under 25 years of age.
UNDERSTANDING GYNAE SWABS
| NG GYNAE SWABS | External skin | Vagina | EndoCervix | PID |
| Bacterial | BV | TV (protozoa) | GC | Chlamydia |
| GC | Chlamydia | Fungal | Candida | Candida |
| Viral | HPV | HSV | HPV | HSV |
BV – Bacterial Vaginosis,
TV – Trichomonas Vaginalis,
GC – Neisseria Gonorrhoeae (Gonococcus),
HPV – Human Papillomavirus,
HSV – Herpes Simplex Virus.
In general, vaginal infections (BV, TV, Candida) cause a lot of discharge compared with
cervical infections (GC, Chlamydia)
Swabs
Three swabs (“triple swabs”) are usually taken to screen for infection in symptomatic
women.
| Swab 1 High vaginal swab (HVS) | Stuart’s Medium | Posterior Fornix | TV, BV (“heavy growth of anaerobes”), Candida & Group B Strep |
| Swab 2 Endocervical swab (ECS) | Stuart’s Medium | Endocervix | GC |
| Swab 3 Chlamydia swab | Chlam swab | Endocervix (cells) | Chlamydia |
Stuart’s medium is basically agar and charcoal, and is a standard transport medium for
most microbiological specimens.
Chlamydia can be identified by immunological techniques (eg. ELISA, ordirect
Immunoflourosence), tissue culture or DNA amplification (PCR, etc). The swab used
will depend on the method of identification used in each particular hospital. Swabs
should be taken from the endocervix, and need to be taken in a particular way (usually
rotated within the endocervix for 10 or 20 seconds) in order to obtain cells.
CERVICITIS (CHLAMYDIA AND NEISSERIA GONORRHOEAE) DIAGNOSIS
- Usually asymptomatic
- Can present with vaginal discharge, low abdominal pain, intermenstrual bleeding of
postcoital bleeding
Diagnosis
- Endocervical or vulvovaginal swab with NAAT, culture or microscopy
In the UK, screening asymptomatic heterosexual patients for gonorrhoea involves using
NAAT. A first pass urine is collected for males and a vulvovaginal swab (which may be
self-taken) is collected for females. If NAAT results show positive for gonorrhoea, a
culture needs to be sent prior to starting antibiotics if possible. This is to test for
susceptibility and resistant strains.
Diagnosis in detail
- Endocervical swab in transport medium (charcoal preferably) is to diagnose
gonorrhoea - Endocervical swab for a chlamydia nucleic acid amplification test (NAAT) is to
diagnose chlamydia - If examination is declined, a self-taken vulvovaginal swab for C. trachomatis and N.
gonorrhoeae for NAAT may be an option and is more sensitive in women than urine
testing.
