Frequently Asked Questions about SPHERUSOL®


SPHERUSOL (Coccidioides immitisSpherule Derived Skin Test Antigen) is prepared and extracted from laboratory cultures of Coccidioides immitisspherules. Spherules are the form of Coccidioidespresent when the fungus is growing in body tissues such as during coccidioidomycosis (i.e., Valley Fever). SPHERUSOL® is packaged as a sterile, ready-to-use aqueous solution in a multi-dose vial (10 tests/vial). SPHERUSOL®does not replace serological testing used by physicians to diagnose coccidioidomycosis.

How Does SPHERUSOL Work?

Most, but not all, people with a history of coccidioidomycosis have developed immunity to Coccidioides. The antigens present in SPHERUSOL elicit a response of the cellular immunity system when injected intradermally. The response, known as delayed-type hypersensitivity (DTH), demonstrates an individual’s immunity to Coccidioidesand the ability of their cellular immune system to produce DTH. Not all people with intact cellular immunity react to coccidioidin preparations and other conditions such as bacterial or viral infections may also interfere; therefore the response to SPHERUSOL is not 100%. Additionally, people with acute or disseminating coccidioidomycosis may not react to SPHERUSOL. SPHERUSOL does not replace serological testing used by physicians to diagnose coccidioidomycosis.

How Is SPHERUSOL® Administered?

SPHERUSOL is used according to the Mantoux Method. It is administered by an intradermal injection of 0.1 mL (cc) to the volar surface of the forearm or outer aspect of the upper arm. Caution must be exercised to avoid subcutaneous or intravenous injections. The injection site is evaluated by a trained health care professional about 48 hours after injection. The site is evaluated for the diameter of observed induration (swelling) and not redness. A positive response to SPHERUSOL is an area of induration of ≥5 mm. The expected response to Spherusol is a local area of inflammation at the site of the skin test. The reaction is usually dime to quarter size reaching maximum diameter between 24 and 48 hours. Larger accelerated reactions can occur, which may require treatment with local cold compresses and anti-inflamatory medication.

Systemic reactions can occur with skin test antigens and in certain individuals these reactions may be life-threatening or cause death. Emergency measures and personnel trained in their use should be immediately available. Patients should be observed for at least 20 minutes following the administration of a skin test. This is not all of the information needed for dosage and administration of SPHERUSOL. See Full Prescribing Information for additional details. For detailed information, see Mantoux Method.

For more information on coccidioidomycosis or Valley Fever:

Centers for Disease Control and Prevention at:

Valley Fever Center for Excellence at:

Kern County Public Health Services at:

Click here to download a copy of the SPHERUSOL Patient Information to provide to your patients.