Sexual Health and Genital Medicine in Clinical Practice

Chapter 2. Routine Investigations Performed in Genitourinary Medicine

Patients attending a GU medicine department for the first time and those presenting with new problems will usually undergo a variety of investigations to check for evidence of infection, both sexually and non-sexually acquired. Many GPs are uncertain which tests are routinely performed and a standard letter from the clinic stating that "the screen for genital infection proved negative" is not particularly instructive. All clinics should be screening for the same infections; however, the specific tests used may vary from clinic to clinic.

Tests routinely performed are as follows.

2.1 MEN

2.1.1 Urethral Swab

 *Gram stain - microscopy

>4 polymorphs per high power field (HPF) = urethritis Gram-negative diplococci within polymorphs - presumptive diagnosis of gonococcal urethritis

 Culture for Neisseria gonorrhoeae (definitive diagnosis of gonorrhea).

 Chlamydia trachomatis detection (usually by nucleic acid amplification test (NAAT) (e.g. PCR or LCR) or enzyme immunoassay (EIA)).

Some clinics have now moved from urethral swab to urine testing for Chlamydia detection. This is likely to become the favored method (certainly by patients) for diagnosing urethral chlamydial infection in men.

2.1.2 *Two Glass Urine Test

This is a time-honored test performed in UK GU medicine clinics, considered by some to be of debatable value. It certainly can help to differentiate a pure urethritis (usually sexually acquired) from a urethritis in association with a cystitis (i.e. a UTI, and not sexually acquired).

 First glass = a first catch urine (50 ml)

 Second glass = second part of urinary stream (50 ml)

Any remaining urine is passed into the urinal.

The following are the interpretation of urine results:

(1) First: clear; second: clear = normal

(2) First: pus (seen as threads, flakes, general haze); second: clear = anterior urethritis (e.g. non-gonococcal urethritis (NGU), gonorrhea)

(3) First: pus; second: pus = posterior urethritis or cystitis (e.g. E. coli, etc.). Send the first glass urine or mid-stream urine (MSU) for culture.

Phosphaturia is a common cause of cloudy urine. The addition of acetic acid will clear the urine when excess phosphates are present whereas the haze remains in cases of pyuria.

The urine may also be checked by dipstix.

Some UK clinics no longer look for urethritis in asymptomatic men. There is however concern that cases of Mycoplasma genitalium urethritis may be missed as culture and nucleic acid amplification tests are not currently routinely available for diagnosing this infection.

The details for women are summarized in Table 2.1.

2.2 MEN AND WOMEN

2.2.1 Syphilis Serology

A blood sample is routinely taken for syphilis serology. There are a number of serological tests available for diagnosing syphilis; commonly used ones include Treponema pallidum antibody, VDRL, and TPHA or TPPA. Screening in GU medicine and antenatal clinics and on donating blood for transfusion has proved successful in keeping syphilis prevalence extremely low in the UK, although in very recent years we have seen an increase in syphilis prevalence in certain areas.

*Indicates tests that may not be currently available or performed in all clinics.

Table 2.1. Routine tests performed on women.

Procedure

Test

Diagnosis

*Vaginal swab

Gram stain: microscopy

Assess bacterial flora Bacterial vaginosis Candidiasis

 

Wet mount: microscopy

Trichomoniasis

Candidiasis

 

Culture

Candida

Trichomonas vaginalis

Cervical swab

*Gram stain: microscopy

>30 polymorphs/HPF suggests cervicitis Gram-negative diplococci inside polymorphs ^ presumptive diagnosis of gonorrhea

 

Culture

Neisseria gonorrhoeae

Cervical swab

Chlamydia trachomatis detection (e.g. EIA, NAAT)

 

Cervical cytology

(if indicated)

 

*Urethral swab

Gram stain: microscopy

Polymorphs may be seen in: chlamydial infection, gonorrhea, trichomoniasis. Gram-negative diplococci inside polymorphs ^ presumptive diagnosis of gonorrhea

 

Culture

Neisseria gonorrhoeae

Urethral swab

Chlamydia trachomatis detection (e.g. EIA, NAAT)

 

*many clinics no longer perform microscopic assessment of vaginal and cervical samples in asymptomatic women and who are not contacts of a partner with an STI.

2.2.2 Hepatitis Screening

Many clinics offer hepatitis B screening and vaccination for injecting drug users and homosexual men and hepatitis C screening for injecting drug users.

2.2.3 HIV Antibody Testing

This is now routinely offered to patients attending GU medicine clinics for screening or testing for STIs and to all women as part of their antenatal care in England and Wales. Some clinics provide a "fast testing service" where results are available "while you wait" or the next day. This aims to encourage individuals to be tested who are otherwise deterred by the prospect of a wait for several days for the results.



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