The Return of Delayed-Type Hypersensitivity Skin Testing for Coccidioidomycosis
August 26 2015
The last commercial skin test for coccidioidomycosis expired in 1999. Since then, clinicians have lacked the diagnostic tools to determine delayed-type hypersensitivity due to Coccidioides spp. — now resulting in almost 150,000 infections per year in the United States alone.
Allermed Laboratories acquired the rights to prepare concentrated antigen for Coccidioides, reformulating the product to exclude thiomersal, associated with dermal sensitisation, and replacing it with phenol. Marketed as Spherusol® and sold by Nielsen Biosciences, this product recently obtained FDA approval via four studies testing safety, sensitivity and specificity. These determined that Spherusol was safe, and had sensitivity and specificity of upwards of 98%, even after prior azole antifungal treatment.
The new product is useful for estimating prevalence of coccidioidomycosis in different populations, particularly in areas where it is not known if Coccidioides is endemic.
A rapid and affordable of skin prick test for Coccidioides will improve diagnosis and therefore prognosis for this infection. Diagnostic options are limited for fungal diseases (primarily being serological, culturing of sputum and radiography), and this test adds to the spectrum of tests available. It can also indicate, without clinical symptoms, that a patient underwent a coccidioidal infection previously and now has immunity to future Coccidioides infections.