Chlamydia

Overview

Nucleic acid amplification tests (NAATs) are the investigation of choice - highest sensitivity and specificity. Specimen type differs by sex and is the highest-yield exam distinction.

First-line investigation by sex
FeatureWomenMen
First-line testNAAT on vulvovaginal swab (self-taken from vaginal introitus)NAAT on first-catch urine (first 10-20 mL)
Why not the alternative?Endocervical swab is less sensitive and requires a clinicianMid-stream urine is less sensitive than first-catch

Feature	Women	Men
First-line test	NAAT on vulvovaginal swab (self-taken from vaginal introitus)	NAAT on first-catch urine (first 10-20 mL)
Why not the alternative?	Endocervical swab is less sensitive and requires a clinician	Mid-stream urine is less sensitive than first-catch

•Rectal or pharyngeal NAAT swab - if receptive anal or oral intercourse reported

•Full STI screen - all confirmed cases offered testing for gonorrhoea, HIV, syphilis, and hepatitis B

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Serology is NOT used for initial diagnosis - lower sensitivity and specificity than NAATs.

Presentation

•Majority of cases are asymptomatic (up to 70% of women, 50% of men)

•Women: mucopurulent vaginal discharge, intermenstrual or post-coital bleeding, dysuria, lower abdominal pain (suggests PID), cervicitis on speculum

•Men: urethral discharge (clear/white), dysuria, unilateral testicular pain and swelling (epididymo-orchitis)

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Post-coital and intermenstrual bleeding in a young woman is a classic chlamydia exam presentation - caused by contact bleeding from the inflamed, friable cervix. Always offer an STI screen.

Management

•First-line (non-pregnant): doxycycline 100 mg twice daily for 7 days

•Second-line (non-pregnant): azithromycin 1 g on day 1, then 500 mg once daily for 2 further days

•Second-line (non-pregnant): ofloxacin 200 mg twice daily for 7 days - contraindicated in pregnancy

•Pregnancy - first-line: azithromycin 1 g on day 1, then 500 mg once daily for 2 days

•Pregnancy - second-line: erythromycin 500 mg four times daily for 7 days (high GI side-effect burden)

•Pregnancy - second-line: amoxicillin 500 mg three times daily for 7 days (penicillins may induce chlamydial latency - discuss with GUM)

•Abstain from sexual intercourse for 7 days after completing treatment and until all partners have also completed treatment

•Partner notification - all partners from the preceding 6 months; approximately two-thirds will test positive

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Doxycycline is contraindicated in pregnancy (teratogenic - impairs fetal bone and tooth development) and in children under 12. Always switch to azithromycin or erythromycin in a pregnant patient.

Follow-up

•Routine test of cure NOT required for most patients

•Pregnant women - test of cure 3-4 weeks after treatment

•Under-25s in England - repeat test 3 months after a positive result (high re-infection rates)

•Persistent symptoms or non-adherence - repeat NAAT at least 3 weeks after completing treatment