Test Catalog

Test Id : ASPBA

Aspergillus Antigen, Bronchoalveolar Lavage

Useful For
Suggests clinical disorders or settings where the test may be helpful

Aiding in the diagnosis of invasive aspergillosis and assessing response to therapy

Method Name
A short description of the method used to perform the test

Enzyme Immunoassay (EIA)

NY State Available
Indicates the status of NY State approval and if the test is orderable for NY State clients.

Yes

Reporting Name
Lists a shorter or abbreviated version of the Published Name for a test

Aspergillus Ag, BAL

Aliases
Lists additional common names for a test, as an aid in searching

Aspergillosis

Invasive Aspergillosis

Platelia Aspergillus Ag

Galactomannan

ASPBA

Specimen Type
Describes the specimen type validated for testing

Lavage

Specimen Required
Defines the optimal specimen required to perform the test and the preferred volume to complete testing

Container/Tube: Sterile, leak-proof container.

Note: Specimen trap collection containers (with suction catheters attached) will be rejected due to high-risk of leakage and contamination upon opening. Avoid use of these for bronchoalveolar lavage specimens.

Specimen Volume: 2 mL

Additional Information: If specimen transfer into an acceptable sterile container is necessary, perform specimen transfer in a biosafety cabinet. Place container in separate sealed plastic bag.

Forms

If not ordering electronically, complete, print, and send Infectious Disease Serology Test Request (T916) with the specimen.

Specimen Minimum Volume
Defines the amount of sample necessary to provide a clinically relevant result as determined by the Testing Laboratory

1.5 mL

Reject Due To
Identifies specimen types and conditions that may cause the specimen to be rejected

Bronchial washing Reject
Thick/viscous/mucoid specimens Reject
Specimen in a nonleak proof container Reject

Specimen Stability Information
Provides a description of the temperatures required to transport a specimen to the performing laboratory, alternate acceptable temperatures are also included

Specimen Type Temperature Time Special Container
Lavage Refrigerated (preferred) 14 days
Frozen 14 days

Useful For
Suggests clinical disorders or settings where the test may be helpful

Aiding in the diagnosis of invasive aspergillosis and assessing response to therapy

Clinical Information
Discusses physiology, pathophysiology, and general clinical aspects, as they relate to a laboratory test

Invasive aspergillosis (IA) is a severe infection that occurs in patients with prolonged neutropenia following transplantation or in conjunction with aggressive immunosuppressive regimens (eg, prolonged corticosteroid use, chemotherapy). The incidence of IA is reported to vary from 5% to 20% depending on the patient population. IA has an extremely high mortality rate of 50% to 80%, due in part to the rapid progression of the infection (ie, 1-2 weeks from onset to death). Approximately 30% of cases remain undiagnosed and untreated at death.

 

Definitive diagnosis of IA requires histopathological evidence of deep-tissue invasion or a positive culture. However, this evidence is often difficult to obtain due to the critically ill nature of the patient and the fact that severe thrombocytopenia often precludes the use of invasive procedures to obtain a quality specimen. The sensitivity of culture in this setting also is low, reportedly ranging from 30% to 60% for bronchoalveolar lavage (BAL) fluid. Accordingly, the diagnosis is often based on nonspecific clinical symptoms (unexplained fever, cough, chest pain, dyspnea) in conjunction with radiologic evidence (computed tomography scan), and a definitive diagnosis is often not established before fungal proliferation becomes overwhelming and refractory to therapy.

 

Recently, a serologic assay was approved by the FDA for the detection of galactomannan, a molecule found in the cell wall of Aspergillus species. Serum galactomannan (Aspergillus antigen) can often be detected a mean of 7 to 14 days before other diagnostic clues become apparent, and monitoring of Aspergillus antigen can potentially allow initiation of preemptive antifungal therapy before life-threatening infection occurs.

 

The clinical utility of Aspergillus antigen testing in BAL specimens as an early prognostic indicator of IA has recently been assessed. These studies demonstrated equivalent or higher sensitivity compared to detection of Aspergillus antigen in serum.(1-4) This assay may be useful in the assessment of therapeutic response as antigen levels typically decline in response to effective antimicrobial therapy.

Reference Values
Describes reference intervals and additional information for interpretation of test results. May include intervals based on age and sex when appropriate. Intervals are Mayo-derived, unless otherwise designated. If an interpretive report is provided, the reference value field will state this.

<0.5 Index

Interpretation
Provides information to assist in interpretation of the test results

A positive result in bronchoalveolar lavage (BAL) fluid supports a diagnosis of invasive, pulmonary aspergillosis. Positive results should be considered in conjunction with other diagnostic procedures, such as microbiologic culture, histological examination of biopsy specimens, and radiographic evidence (see Cautions).

 

A negative result in BAL fluid does not rule out the diagnosis of invasive aspergillosis (IA). Patients at risk of IA should be monitored twice a week for Aspergillus antigen levels in serum until determined to be clinically unnecessary.

 

Aspergillus antigen levels typically decline in response to effective antimicrobial therapy.

Cautions
Discusses conditions that may cause diagnostic confusion, including improper specimen collection and handling, inappropriate test selection, and interfering substances

False-positive results are reported to occur at rates of 8% to 14% with this assay when performed on serum. Numerous foods (eg, pasta, rice, etc) contain galactomannan. It is thought that damage to the gut wall by cytotoxic therapy, irradiation, or graft-versus-host disease enables translocation of the galactomannan from the gut lumen into the blood and may be partially responsible for the high false-positive rate of this assay when serum is tested. Whether false-positive results in bronchoalveolar lavage (BAL) fluid are associated with the consumption of certain foods, as is observed in serum samples, remains to be determined.

 

Other genera of fungi such as Penicillium and Paecilomyces have shown reactivity with the rat EBA-2 monoclonal antibody used in the assay. These species are rarely implicated in invasive fungal disease. Specimens containing Histoplasma antigen may cross-react in the Aspergillus antigen assay. Cross-reactivity with Alternaria species also has been reported.

 

Semisynthetic antibiotics such as piperacillin, amoxicillin, and Augmentin, which are based on natural compounds derived from the genus Penicillium, have been demonstrated to cross-react with the rat EBA-2 monoclonal antibody used in the assay.

 

The specificity of the assay for Aspergillus species cannot exclude the involvement of other fungal pathogens with similar clinical presentations such as Fusarium, Alternaria, and Mucorales.

 

The performance of the assay has not been evaluated other specimen types such as urine or cerebrospinal fluid.

 

The assay may exhibit reduced detection of Aspergillus antigen in patients with chronic granulomatous disease and Job syndrome.

 

The concomitant use of antifungal therapy in some patients with invasive aspergillosis may result in reduced sensitivity of the assay.

 

False-positive results are possible in patients receiving PLASMA-LYTE for intravenous hydration or if PLASMA-LYTE is used during bronchoscopy for the collection of BAL fluid.

Supportive Data

In clinical studies submitted to the Food and Drug Administration (FDA), the sensitivity of the test for serum was reported to be 81% for proven or probable invasive aspergillosis (n=31 patients), and the specificity was 89% (n=148 patients). The positive and negative predictive values were reported as 68% and 96% respectively, based on an average prevalence of 14% in the study population. In a low prevalence population (5%), the positive predictive value decreases to 31%; the negative predictive value remains at 96%.(Package insert: Platelia Aspergillus EIA. Bio-Rad; 6/2003).

 

Accuracy:

The performance characteristics of the Platelia Aspergillus enzyme immunoassay (EIA) for the detection of galactomannan in bronchoalveolar lavage (BAL) fluid were validated at Mayo Clinic Laboratories by comparison of results obtained from an outside reference laboratory using the same assay. These studies demonstrated 95.6% (240/251) agreement between sites (Table 1).

 

Table 1: Comparison of Platelia Aspergillus Antigen results at Mayo Clinic Laboratories and an outside reference laboratory using BAL fluid (n=251).

 

Outside reference lab Aspergillus antigen result

MCL Aspergillus antigen result

Positive

Negative

Positive

24

1

Negative

10

216

Percent Agreement: 95.6% (240/251) (95% Cl; 92.2-97.6)

Kappa value: 0.79

 

For 10 of the 11 discordant results, testing at Mayo Clinic Laboratories correlated with either serum Aspergillus antigen levels or fungal culture.

 

Precision:

Intra- and interassay precision was tested for negative, midrange and high-positive, and spiked bronchoalveolar lavage (BAL) specimens. The mean index values, standard deviation and percent coefficient of variation were all acceptable, indicating excellent precision. (Table 2-3)

 

Table 2: Intra-assay precision studies

 

Mean index

Standard deviation

% Coefficient of variation

Negative

0.23

0.05

22.1

Mid-positive

2.23

0.16

  6.9

High positive

4.29

0.43

  9.9

Positive: >0.5

Negative: <0.5

 

Table 3: Inter-assay precision studies

 

Mean Index

Standard Deviation

% Coefficient of variation

Negative

0.20

0.05

25.5

Mid-positive

2.32

0.39

17.1

High positive

4.45

0.84

18.9

Positive: >0.5

Negative: <0.5

 

Analytical Specificity:

Cross-reactivity studies were performed by testing analyte-negative BAL specimens that had been spiked with varying concentrations of positive control material for the following organisms: Histoplasma capsulatum, Blastomyces dermatitidis, or Cryptococcus neoformans. These studies demonstrated that high concentrations of Histoplasma and Blastomyces antigen in BAL may yield positive results by the Platelia Aspergillus antigen assay. This has been demonstrated in prior published studies,(5) and it is a known limitation of this test that there may be cross-reactivity with dimorphic fungal pathogens.

 

In addition to the studies above, an analyte-negative BAL specimen was spiked with a pleural fluid that was known to be positive for Streptococcus pneumoniae antigen. This spiked- specimen was tested by the Platelia assay and was negative at all dilutions tested.

Clinical Reference
Recommendations for in-depth reading of a clinical nature

1. Park SY, Lee S, Choi S, et al: Aspergillus galactomannan antigen assay in bronchoalveolar lavage fluid for diagnosis of invasive pulmonary aspergillosis. J Infect. 2010;61:492-498

2. Husain S, Clancy CJ, Nguyen MH, et al: Performance characteristics of the Platelia aspergillus enzyme immunoassay for detection of Aspergillus galactomannan antigen in bronchoalveolar lavage fluid. Clin Vaccine Immunol. 2008;15(12):1760-1763

3. Meersseman W, Lagrou K, Maertens J, et al: Galactomannan in bronchoalveolar lavage fluid a tool for diagnosing aspergillosis in intensive care unit patients. Am J Respir Crit Care Med. 2008;177:27-34

4. Becker MJ, Lugtenburg EJ, Cornelissen JJ, Van Der Schee C, Hoogsteden HC, De Mari Se: Galactomannan detection in computerized tomography-based bronchoalveolar lavage fluid and serum in haematological patients at risk for invasive pulmonary aspergillosis. Br J Haematol. 2003;121:448-457

5. Xavier MO, Pasqualotto AC, Cardoso IC, Severo LC: Cross-reactivity of Paracoccidioides brasiliensis, Histoplasma capsulatum, and Cryptococcus species in the commercial Platelia Aspergillus enzyme immunoassay. Clin Vaccine Immunol. 2009 Jan;16(1):132-133

Method Description
Describes how the test is performed and provides a method-specific reference

The Platelia Aspergillus enzyme immunoassay ) is a 1-stage immunoenzymatic sandwich microplate assay that detects galactomannan in bronchoalveolar lavage  specimens. The assay uses the rat monoclonal antibody EBA-2, which is directed against Aspergillus galactomannan. The monoclonal antibody is used 1) to coat the wells of the microplate and bind the antigen and 2) as the detector antibody in the conjugate reagent (peroxidase-linked monoclonal antibody).

 

Samples are heat-treated in the presence of EDTA in order to dissociate immune complexes and to precipitate proteins that could possibly interfere with the test. The treated samples and conjugate are added to the wells coated with the monoclonal antibody and incubated. A monoclonal antibody-galactomannan-monoclonal antibody/peroxidase complex is formed in the presence of Aspergillus antigen.

 

The strips are washed to remove any unbound material, and the substrate solution is added, which will react with the complex bound to the well to form a blue color reaction. The enzyme reaction is stopped by the addition of acid, which changes the blue color to yellow. The optical absorbance of specimens and controls is determined with a spectrophotometer set at 450 nm and 620/630 nm wavelengths.

 

Negative, cutoff (low-positive), and high-positive controls are analyzed each time the assay is performed. The presence or absence of Aspergillus (galactomannan) antigen in the test sample is determined by calculation of an index for the specimen. The index is the optical density (OD) value of the specimen divided by the mean OD of wells containing the cutoff control serum (low-positive control).(Package insert: Platelia Aspergillus EIA. Bio-Rad Laboratories; 10/2013)

PDF Report
Indicates whether the report includes an additional document with charts, images or other enriched information

No

Day(s) Performed
Outlines the days the test is performed. This field reflects the day that the sample must be in the testing laboratory to begin the testing process and includes any specimen preparation and processing time before the test is performed. Some tests are listed as continuously performed, which means that assays are performed multiple times during the day.

Monday through Friday, Sunday

Report Available
The interval of time (receipt of sample at Mayo Clinic Laboratories to results available) taking into account standard setup days and weekends. The first day is the time that it typically takes for a result to be available. The last day is the time it might take, accounting for any necessary repeated testing.

1 to 2 days

Specimen Retention Time
Outlines the length of time after testing that a specimen is kept in the laboratory before it is discarded

14 days

Performing Laboratory Location
Indicates the location of the laboratory that performs the test

Rochester

Fees
Several factors determine the fee charged to perform a test. Contact your U.S. or International Regional Manager for information about establishing a fee schedule or to learn more about resources to optimize test selection.

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Test Classification
Provides information regarding the medical device classification for laboratory test kits and reagents. Tests may be classified as cleared or approved by the US Food and Drug Administration (FDA) and used per manufacturer instructions, or as products that do not undergo full FDA review and approval, and are then labeled as an Analyte Specific Reagent (ASR) product.

This test has been cleared, approved, or is exempt by the US Food and Drug Administration and is used per manufacturer's instructions. Performance characteristics were verified by Mayo Clinic in a manner consistent with CLIA requirements.

CPT Code Information
Provides guidance in determining the appropriate Current Procedural Terminology (CPT) code(s) information for each test or profile. The listed CPT codes reflect Mayo Clinic Laboratories interpretation of CPT coding requirements. It is the responsibility of each laboratory to determine correct CPT codes to use for billing.

CPT codes are provided by the performing laboratory.

87305

LOINC® Information
Provides guidance in determining the Logical Observation Identifiers Names and Codes (LOINC) values for the order and results codes of this test. LOINC values are provided by the performing laboratory.

Test Id Test Order Name Order LOINC Value
ASPBA Aspergillus Ag, BAL 62467-6
Result Id Test Result Name Result LOINC Value
Applies only to results expressed in units of measure originally reported by the performing laboratory. These values do not apply to results that are converted to other units of measure.
61009 Aspergillus Ag, BAL 62467-6

Test Setup Resources

Setup Files
Test setup information contains test file definition details to support order and result interfacing between Mayo Clinic Laboratories and your Laboratory Information System.

Excel | Pdf

Sample Reports
Normal and Abnormal sample reports are provided as references for report appearance.

Normal Reports | Abnormal Reports

SI Sample Reports
International System (SI) of Unit reports are provided for a limited number of tests. These reports are intended for international account use and are only available through MayoLINK accounts that have been defined to receive them.

SI Normal Reports | SI Abnormal Reports