Tests
1st tests to order
swab for microbiology (Gram stain and culture) and Nucleic acid amplification test (NAAT)
Test
KOH preparation for Candida may be indicated if this agent/fungal infection is suspected or needs to be excluded.
NAAT for: C trachomatis, Mycoplasma genitalium, Neisseria gonorrhoeae, Treponema pallidum.
Chocolate agar can be used to culture Neisseria gonorrhoeae.
Result
may be positive for infection; the presence of Candida or other organism does not exclude another dermatosis e.g., lichen sclerosus
swab for virology
Test
Preferred tests are polymerase chain reaction (PCR) or other nucleic acid amplification tests (NAATs), or viral culture.
Result
positive PCR or culture
dark-field microscopy
Test
Not usually available outside specialist settings. A single negative result does not exclude infection; ideally 3 negative examinations on different days are required.
Result
may be positive for syphilis bacteria
Tests to consider
skin biopsy
Test
May be indicated to clarify diagnostic uncertainty.[1]
It is important to ensure that the right specimen is obtained from the appropriate site and to provide the pathologist with adequate information.[41]
Avoid biopsying the glans (unless there is not suitable lesion or rash elsewhere) and near the frenulum where the urethra is very close to the surface.
Result
histopathology findings consistent with causative condition; negative or nonspecific results do not exclude an inflammatory dermatosis such as lichen sclerosus or premalignant condition such as penile intraepithelial neoplasia or frank carcinoma.
patch testing
Test
Performed if allergic contact dermatitis is suspected or needs to be excluded.
Interpreted by a dermatologist in a patch test clinic setting.
Result
may be positive in allergic contact dermatitis
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