What is the role of lab testing in the diagnosis of paronychia?

Updated: Oct 09, 2020
  • Author: Elizabeth M Billingsley, MD; Chief Editor: William D James, MD  more...
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The diagnosis of paronychia is based primarily on patient history and physical examination. Some laboratory studies, however, can be useful.

Fluctuant paronychia usually results from bacterial infection; therefore, routine Gram staining and culture can help in identifying the causative organism.

Potassium hydroxide (KOH) 5% smears may be helpful in diagnosing paronychia if Gram staining results are negative or if candidal infection is suspected, as in chronic paronychia. If Gram staining results are negative, the KOH preparation may demonstrate pseudomycelia and clusters of grapelike yeast cells. KOH wet mounts from scrapings or discharge may show hyphae.

Tzanck smears may be performed if herpetic whitlow is suspected. Smears should be performed by using base scrapings of an unroofed vesicle. The presence of multinucleated giant cells, often with visible viral inclusions, indicates a positive result.

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