Chancroid in Emergency Medicine Workup

Updated: Jun 17, 2019
  • Author: Kristine Song, MD; Chief Editor: Barry E Brenner, MD, PhD, FACEP  more...
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Workup

Approach Considerations

Per CDC guidelines (2015), a diagnosis of chancroid requires satisfaction of all of the following conditions: [15]

  • The patient has one or more painful genital ulcers.
  • The clinical presentation, appearance of genital ulcers, and, if present, regional lymphadenopathy are typical of chancroid.
  • The patient has no evidence of T pallidum infection on darkfield examination of ulcer exudate or on a serologic test for syphilis performed at least 7 days after the onset of ulcers.
  • The HSV PCR test or HSV culture results performed on the ulcer exudate are negative.

Physical examination findings should include both of the following to suggest a diagnosis of chancroid: [16]

  • Painful genital ulcer
  • Tender suppurative inguinal adenopathy
Next:

Laboratory Studies

Microbiological diagnosis should be obtained in all cases of suspected chancroid, if possible. [9]

For definitive diagnosis of chancroid by H ducreyi, obtain the following: [9, 15]

  • Gram stain of the ulcer exudate
  • Culture of ulcer exudate on special media (if possible, multiple cultures should be obtained to enhance the likelihood of recovering the organism)
  • If possible, antibiotic sensitivity testing from the culture

Other necessary tests to obtain include the following: [15]

  • Syphilis serology, darkfield examination, or PCR testing, if available
  • Culture or PCR testing for genital herpes
  • Serologic testing for type-specific HSV antibody
  • HIV testing

Culture is unreliable and insensitive. Sensitivities have been found to be between 50% and 100%. [17] 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". [14] 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%. [17] 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.

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