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Test ID: HBRP Histoplasma capsulatum/Blastomyces species, Molecular Detection, PCR, Varies

Reporting Name

Histoplasma/Blastomyces PCR

Useful For

Rapid detection of Histoplasma capsulatum and Blastomyces dermatitidis DNA

 

An aid in the rapid diagnosis of histoplasmosis and blastomycosis

Clinical Information

Infections with Blastomyces dermatitidis and Histoplasma capsulatum cause a variety of clinical manifestations ranging from self-limited, mild pulmonary illness to potentially life-threatening, disseminated disease. Patients at risk for disseminated disease include neonates and immunosuppressed individuals, particularly those with AIDS, hematologic malignancies, or a recent transplant. Primary infections are acquired through inhalation of microconidia that are present in the environment. In the United States, most cases of blastomycosis and histoplasmosis occur along the Ohio and Mississippi River valleys.

 

The gold standard for diagnosis of blastomycosis and histoplasmosis remains isolation of the organisms in culture. Although sensitive, recovery in culture and subsequent identification may require days to weeks. The organisms can be identified after growth in culture using traditional macro- and microscopic morphologic techniques or through the use of nucleic acid hybridization probes. Hybridization probe-based procedures are rapid and demonstrate good sensitivity and specificity from culture, although some cross-reactivity with relatively uncommon fungal organisms has been reported. Additional diagnostic tests that can be utilized for these organisms include stains, histopathology, serology, and antigen detection with each of these methods offering advantages and limitations depending on the stage of the illness and the status of the patient. Fungal stains (eg, calcofluor white) offer a rapid diagnostic approach, but demonstrate poor sensitivity and specificity. Serologic tests such as complement fixation and immunodiffusion are noninvasive, but are laborious, subjective, and may show low sensitivity, especially in immunocompromised hosts. Antigen detection also offers a noninvasive approach, but has been demonstrated to show cross-reactivity with antigens from closely related fungal species.

 

Molecular techniques have been established as sensitive and specific methods for the diagnosis of infectious diseases and have the added advantage of a rapid turnaround time for results. Due to the limitations of conventional diagnostic methods for blastomycosis and histoplasmosis, a single tube, real-time PCR assay was developed and verified for the detection and differentiation of B dermatitidis/gilchristii and H capsulatum directly from clinical specimens.

Interpretation

A positive result for Histoplasma capsulatum indicates presence of Histoplasma DNA; a positive result for Blastomyces dermatitidis/gilchristii indicates presence of Blastomyces DNA.

 

A negative result indicates absence of detectable H capsulatum and B dermatitidis/gilchristii DNA. Fungal culture has increased sensitivity over this PCR assay and should always be performed when the PCR is negative.

Testing Algorithm

See Meningitis/Encephalitis Panel Algorithm in Special Instructions.

Analytic Time

1 day

Day(s) and Time(s) Performed

Monday through Friday, 3 times per week

Clinical Reference

1. Kauffman CA: Histoplasmosis. Clin Chest Med 2009;30:217-225

2. Wheat LJ, Freifeld AG, Kleiman MB, et al: Clinical practice guidelines for the management of patients with histoplasmosis: 2007 update by the Infectious Diseases Society of America. Clin Infect Dis 2007;45:807-825

3. Chapman SW, Bradsher RW Jr, Campbell GD Jr, et al: Practice guidelines for the management of patients with blastomycosis. Infectious Diseases Society of America. Clin Infect Dis 2000;30:679-683

Method Name

Real-Time Polymerase Chain Reaction (PCR)

Specimen Type

Varies


Advisory Information


Urine is not an acceptable source for this assay. Studies indicate that Histoplasma DNA is not routinely found in the urine of patients with disseminated histoplasmosis. Therefore, the UHIST / Histoplasma Antigen, Urine is the recommended test for this specimen source.



Additional Testing Requirements


This test should always be performed in conjunction with fungal culture, order FGEN / Fungal Culture, Routine.



Shipping Instructions


Specimen must arrive within 7 days of collection; specimens received after 7 days will be rejected.

 

NALC/NaOH-digested specimen must arrive within 7 days of digestion.



Necessary Information


Specimen source is required.



Specimen Required


The high sensitivity of amplification by PCR requires the specimen to be processed in an environment in which contamination of the specimen by Histoplasma or Blastomyces species DNA is not likely.

 

Submit only 1 of the following specimens:

 

Specimen Type: Body fluid

Sources: Body, CSF, bone marrow

Container/Tube: Sterile container

Specimen Volume: 1 mL

 

Specimen Type: Respiratory

Sources: BAL, bronchial washing, sputum

Container/Tube: Sterile container

Specimen Volume: 1 mL

 

Specimen Type: Tissue or bone

Container/Tube: Sterile container

Specimen Volume: 5-10 mm

Collection Instructions: Collect a fresh tissue or bone specimen.

 

Acceptable:

Specimen Type: NALC/NaOH-digested respiratory specimens

Sources: Lavage fluid, bronchial washing, gastric washing, respiratory fluid, sputum, or tracheal secretion

Container/Tube: Sterile container

Specimen Volume: 2 mL

Collection Instructions:

1. Submit digested specimen treated with NALC/NaOH.

2. Clearly indicate on container and order form that specimen is a digested specimen.


Specimen Minimum Volume

Body Fluid or Respiratory Specimen: 0.5 mL

Specimen Stability Information

Specimen Type Temperature Time Special Container
Varies Refrigerated (preferred) 7 days
  Ambient  7 days
  Frozen  7 days

Reference Values

Not applicable

Test Classification

This test was developed and its performance characteristics determined by Mayo Clinic in a manner consistent with CLIA requirements. This test has not been cleared or approved by the U.S. Food and Drug Administration.

CPT Code Information

87798 x 2

LOINC Code Information

Test ID Test Order Name Order LOINC Value
HBRP Histoplasma/Blastomyces PCR 81653-8

 

Result ID Test Result Name Result LOINC Value
SRC78 Histo/Blasto Source 31208-2
32457 Histo/Blasto Result 81653-8

Forms

If not ordering electronically, complete, print, and send a Microbiology Test Request (T244) with the specimen.

Mayo Clinic Laboratories | Neurology Catalog Additional Information:

mml-CNS-Infections, mml-Pediatric