Histoplasma Antigen Urine
Histoplasmosis is a common fungal infection in the United States that causes respiratory illness. Symptoms include fever, headache, and respiratory symptoms, although infected persons can remain asymptomatic. Most patients will recover regardless of treatment, but severe disease can lead to respiratory failure and should be treated. Immunocompromised patients are at high risk for developing systemic histoplasmosis.
Illness usually is acquired from inhalation of soil contaminated with bird or bat droppings. Endemic areas include the midwestern states, particularly the Mississippi and Ohio River valleys. Human-to-human transmission does not occur.
Acute infection is detected by performing an enzyme immunoassay for Histoplasma capsulatum antigen on urine samples. A confirmed case of histoplasmosis is defined as a serum or urine test positive for H. capsulatum, regardless of a person's symptoms.
Histoplasma antigen is detected using an enzyme immunoassay that detects Histoplasma galactomannan in urine. Reference value is a negative result which is consistent with the absence of infection. Presence of Histoplasma antigen in urine is indicative of current or recent infection with Histoplasma capsulatum. Indeterminate results should be confirmed. Clinical decisions should not be based on an indeterminate result alone.
Urine histoplasma antigen can be used to monitor therapy. Declining levels are indicative of response to antifungal therapy. Low-levels of antigenmay persist for months following resolution of infection.
Cross-reactivity with other fungal infections, such as Blastomyces dermatitidis, may occur.
Reference ranges for urine antigen are:
Negative: 0.00 - 0.10
Indeterminate: 0.11-0.49
Positive: 0.50 or higher
Specimen requirement is 3 mL of a random urine.
