The work-up for this etiology must be guided by the clinical symptoms:
– Syphilis chancres are 5 to 20 mm in diameter, and they have an indurated base and sharp borders. They often occur alone and are completely painless.
– The soft chancre due to Haemophilus ducreyi has a smooth, edematous base and irregular borders. In one-third of cases, the ulcerations are multiple and are the result of self-inoculation. These ulcerations are painful.
– Ulcerations of herpetic origin are also painful and multiple but are smaller and develop from vesicles.
– Soak the gauze dressing in sterile normal saline.
– Clean the ulceration.
– Using a sterile lancet, leak out the serous fluid from the chancre without making it bleed.
– Obtain a swab sample and take it to the laboratory.
Syphilis serology is very often added for making differential diagnoses.