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HelpEpic Test Code LAB3123 Aspergillus (Galactomannan) Antigen, Serum
Additional Codes
MML Code: ASPAG
NY State Approved
YesPerforming Laboratory
Mayo Clinic Laboratories in Rochester
Reporting Name
Aspergillus Ag, SMethod Name
Enzyme Immunoassay (EIA)
Specimen Stability Information
| Specimen Type | Temperature | Time | Special Container |
|---|---|---|---|
| Serum SST | Refrigerated (preferred) | 14 days | SERUM GEL TUBE |
| Frozen | 14 days | SERUM GEL TUBE |
Ordering Guidance
For bronchoalveolar lavage specimens, order ASPBA / Aspergillus Antigen, Bronchoalveolar Lavage.
Specimen Required
Container/Tube: Serum gel (red-top tubes are not acceptable)
Specimen Volume: 1.5 mL
Collection Instructions:
1. Avoid exposure of specimen to atmosphere to prevent sample contamination from environment.
2. Centrifuge and send specimen in original tube. Do not aliquot or open tube.
Blood Tube Draw Volume
Min 50% draw volume
Specimen Type
Serum SSTSpecimen Minimum Volume
1 mL
Reference Values
<0.5 index
Reference values apply to all ages.
Report Available
1 to 4 daysDay(s) Performed
Monday through Friday, Sunday
CPT Code Information
87305
Reject Due To
| Gross hemolysis | Reject |
| Gross lipemia | Reject |
Useful For
Aiding in the diagnosis of invasive aspergillosis
Assessing response to therapy
Clinical Information
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 usage, 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. 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 is low, reportedly ranging from 30% to 60% for bronchoalveolar lavage 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); a definitive diagnosis is often not established before fungal proliferation becomes overwhelming and refractory to therapy.
Recently, a serologic assay was approved by the US Food and Drug Administration for the detection of galactomannan, a molecule found in the cell wall of Aspergillus species. Serum galactomannan can often be detected a mean of 7 to 14 days before other diagnostic clues become apparent, and monitoring of galactomannan can potentially allow initiation of preemptive antifungal therapy before life-threatening infection occurs.
Interpretation
A positive result supports a diagnosis of invasive aspergillosis (IA). 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 does not rule out the diagnosis of IA. Repeat testing is recommended if the result is negative but IA is clinically suspected. Patients at risk of IA should have a baseline serum tested and should be monitored twice a week for increasing galactomannan antigen levels.
Galactomannan antigen levels may be useful in the assessment of therapeutic response. Antigen levels decline in response to antimicrobial therapy.
Cautions
False-positive results are reported to occur at rates of 8% to 14% with this assay. For all positive patients, it is recommended that a new aliquot of the same specimen be repeated, as well as collection of a new specimen from the patient for follow-up testing. Two or more consecutive positive results should be obtained from separately collected specimens before the patient is considered to have a positive Aspergillus antigen test.
Numerous foods (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.
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. Cross reactivity with Alternaria species has also been reported.
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 with neonate serum specimens or for use with plasma or other specimen types such as urine or cerebrospinal fluid.
The assay may exhibit reduced detection of galactomannan in patients with chronic granulomatous disease or autosomal dominant hyper-IgE syndrome (formerly known as Job syndrome).
The concomitant use of antifungal therapy in some patients with invasive aspergillosis may result in reduced sensitivity of the assay.
False-positive galactomannan results are possible in patients receiving PLASMA-LYTE for intravenous hydration or if PLASMA-LYTE is used during bronchoscopy for the collection of bronchoalveolar lavage fluid.
Specimens containing Histoplasma antigen may cross-react in the Aspergillus galactomannan assay.
Potential false-positive results exhibited with serum specimens when digestive enzymes of fungal origin, like Nortase, are used for enzyme substitution therapy in exocrine pancreatic insufficiency in intensive care unit patients.(1)
Supportive Data
In clinical studies submitted for the US Food and Drug Administration-approval process, the sensitivity of the test was reported to be 81% for proven/provable 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 Laboratories; 06/2003)
Specimen Retention Time
2 weeksForms
If not ordering electronically, complete, print, and send 1 of the following forms with the specimen:
-General Request (T239)