Type of test Blood, microscopic examination

 Normal findings

No antibodies detected

 β-D-glucan:

Negative : < 60 pg/mL

 Indeterminate : 60-79 pg/mL

 Positive : ≥ 80 pg/mL

Culture: no growth in 24 days

Gram stain: no fungus seen

Test explanation and related physiology

Few fungal diseases can be diagnosed clinically; many are diagnosed by isolating and identifying the infecting fungus in the clinical laboratory. Fungal infections can be superficial, subcutaneous, or systemic (deep). The systemic fungal infections (mycoses) are the most important, for which serologic antibody testing is performed. In general, mycoses are caused by the inhalation of airborne fungal spores. In the United States, the most serious fungal infections are coccidioidomycosis, blastomycosis, histoplasmosis, and paracoccidioidomycosis. These infections start out as primary pulmonary infections. Aspergillus, Candida, and Cryptococcus systemic infections usually affect only those with compromised immunity.

Fungal antibody testing is not highly reliable. In general, this testing is used for screening for antibodies to dimorphic fungi (Blastomyces, Coccidioides, Histoplasma spp.) and the antigen of Cryptococcus neoformans during acute infection. Antibodies are present in only about 70% to 80% of infected patients. When positive, they merely indicate that the person has an active or has had a recent fungal infection. These antibodies can be identified in the blood or cerebrospinal fluid (CSF). Antibodies can be tested singularly or as a fungal panel.

(1,3)-β-D-glucan is used to support the diagnosis of invasive fungal disease (IFD) in at-risk patients. Normally, serum contains low levels of (1,3)-β-D-glucan, presumably from yeasts present in the alimentary and GI tract. D-glucan becomes elevated well in advance of conventional clinical signs and symptoms of IFD. As opportunistic infections, IFDs are common among patients with hematologic malignancies or AIDS. They account for a growing number of nosocomial infections, particularly among organ transplant recipients and other patients receiving immunosuppressive treatments. (1,3)-β-D-glucan is produced by most invasive fungal organisms. Blastomyces and Cryptococcus produce very low levels of (1,3)-β-D-glucan. Mucoromycetes do not produce (1,3)-β-D-glucan. It is important to note that negative results do not exclude fungal etiology, especially in the early stages of infection.

Correlation of the patient clinical condition with culture results is necessary. Fungus can be cultured from blood, body fluids, CSF, fresh tissue, bronchopulmonary secretions, or swabs of the ear, nose, and throat or from urine. Accurate fungal culture is labor intensive and requires a highly experienced laboratory. Results are not available quickly.

Interfering factors

• False-positive results can occur if a patient’s intestinal tract is colonized with Candida spp.

• False-positive results occur in patients on hemodialysis using cellulose membranes.

 • False-negative results occur in serum that is hemolyzed, icteric, lipemic, or turbid.

 Procedure and patient care

 • See inside front cover for Routine Blood Testing.

• Fasting: no

• Blood tube commonly used: red or serum separator

• Indicate on the laboratory slip the particular antibody or panel of antibodies that are to be tested.

• Because some patients with fungal infection may be immunocompromised, instruct them to check for signs of infection at the venipuncture site.

 Abnormal findings

 Increased levels

- Acute fungal infection

- Previous systemic exposure to fungal disease