Chancroid in Emergency Medicine Workup

Updated: Jul 26, 2016
  • Author: Andrew D Nguyen, MD; Chief Editor: Barry E Brenner, MD, PhD, FACEP  more...
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Workup

Laboratory Studies

Culture is unreliable and insensitive. Sensitivities have been found to be between 50% and 100%. [14] Use of a special medium is required to culture H ducreyi due to its heme dependence. The growth temperature is also lower (33°C) than most organisms. If cultures are going to be positive, they usually grow organisms within 3 days.

Polymerase chain reaction (PCR) is 96-100% sensitive and 97-98% specific. [6] However, PCR is not usually performed on site, thereby causing a delay in making the diagnosis. The expense is another factor. PCR directed against 1 of 2 genomic segments (either the ribosomal RNA gene, rrs-rrl ribosomal intergenic spacer region, or the GroEL gene, which encodes a heat shock protein) can be used.

Gram stain is similar to PCR in the time it takes and the delay in diagnosis and treatment. Microbiologists have described H ducreyi as looking like "schools of fish", "railroad tracks", and "fingerprints". [13] Histologic findings include neutrophils, fibrin, erythrocytes, and necrotic tissue.

Immunochromatography is a rapid diagnostic test that usually takes approximately 15 minutes to perform. Immunochromatography tests use monoclonal antibodies to the hemoglobin receptor of H ducreyi, hgbA, an outer membrane protein. Patterson reported this test to have a specificity of 100%. [14] Furthermore, these tests are easily performed, relatively inexpensive, and stable in several climates. The downside, however, is that the sensitivity has been found to be comparably poor. Availability of this test is limited by this.

The syndromic management approach by the World Health Organization and US Centers for Disease Control and Prevention (CDC) suggests a probable positive diagnosis if the patient has all of the following criteria: one or more painful genital ulcers, no evidence of syphilis by darkfield examination of ulcer exudate or serologic testing greater than 7 days after ulcer onset, negative testing for herpes simplex virus, and clinical presentation consistent with chancroid. [11]