Fungal – Serology

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Background
Fungal serology (antibody) testing is available at Public Health Ontario. Please note, the specific serological test must be clearly indicated on the requisition form. Fungal infections can be challenging to diagnose as symptoms are often non-specific and can mimic bacterial, viral, other fungal infections or malignancy. Culture remains the gold standard for the diagnosis of most invasive fungal infections; however, results of fungal serological tests can be used to aid in the diagnosis and/or management of specific fungal infections and fungal allergies.

Serological testing is available for the following fungal pathogens. The specific fungal serological test must be clearly indicated on the requisition form:

Aspergillus
Ubiquitous environmental molds which people inhale each day. While invasive disease is typically restricted to immunocompromised individuals, immunocompetent individuals can have certain allergic manifestations or develop chronic pulmonary aspergillosis (CPA).
Histoplasma capsulatum, Blastomyces dermatitidis complex and Coccidioides immitis/posadasii
Endemic, dimorphic fungi can infect otherwise healthy individuals. Most infected individuals are exposed by inhaling fungal spores from the environment and are present with initial clinical symptoms of respiratory illness. Left untreated, these infections can disseminate, particularly in the immunocompromised.

Each of these endemic, dimorphic fungi have distinct geographic distributions:

H. capsulatum can be found throughout Canada but is highly endemic in eastern Ontario and Quebec along the St. Lawrence River valley. The Ohio and Mississippi river valleys are also endemic regions. H. capsulatum is also known to be associated with bird and bat droppings.
B. dermatitidis is endemic to large areas of North America, and in Canada is most common in Manitoba, Quebec, and Ontario, however cases have also been reported in other provinces. The north-western part of Ontario is a hyperendemic area of B. dermatitidis complex although cases are known to have been acquired in the southern and eastern parts of the province as well. In the USA, Michigan, Wisconsin, Minnesota and the Mississippi and Ohio River valleys are known endemic regions. Blastomycosis cases are often linked to exposure to water, decaying wood or soil.
Coccidioides immitis/posadasii is endemic to the southwestern USA, or northern Mexico and causes coccidioidomycosis (Valley Fever). It is not endemic to Canada but can be seen in people that have returned from travel to endemic areas.

For information on fungal culture please refer to:

Updates
Effective September 1, 2025, the specific fungal serological test(s) must be specified on the requisition form. Requests for ‘Fungal Serology’ will be cancelled if the specific fungus (fungi) being requested is not indicated. For details, refer to the Specimen Collection and Handling section.

* Copie d'impression non contrôlée. Valide uniquement le jour de l'impression : 22 oct. 2025.

Testing Indications

Aspergillus serology test may be useful in the diagnosis and monitoring of immunocompetent, adult patients where allergic bronchopulmonary aspergillosis (ABPA), chronic pulmonary aspergillosis (CPA), or fungal sinusitis are due to Aspergillus.

Serologic testing for Histoplasma capsulatum is indicated in patients with suspected pulmonary or disseminated histoplasmosis, especially in those with subacute or chronic symptoms, and in endemic areas.^1,2

Blastomycosis is an invasive fungal disease that often presents as community-acquired pneumonia in primary and urgent care settings. It is endemic in parts of Canada, including Ontario, Manitoba and Quebec as well as several north-eastern U.S. states. Serologic testing is not recommended as a diagnostic assay for blastomycosis due to low sensitivity²; for diagnosis of blastomycosis submission of specimens for microscopy and culture are recommended [Refer to: Mycology - Fungal Culture - Systemic]. Serology may aid in determining if a patient has been exposed to Blastomyces but should not be used as a stand-alone test for diagnosis. ²

Serologic testing for Coccidioides species is indicated in patients with suspected pulmonary or disseminated coccidioidomycosis, especially those with respiratory symptoms or systemic signs in endemic regions (e.g., Southwestern U.S.) ^2,3

Acceptance/Rejection Criteria

Specimens may be subject to rejection if they are:

not the appropriate sample type
have insufficient volume
are not accompanied by relevant patient information or clinical history
or if no specific fungal agent is requested for serologic testing on the requisition.

Specimen Collection and Handling

Specimen Requirements

Test Requested	Required Requisition(s)	Specimen Type	Minimum Volume	Collection Kit
Aspergillus Serology^1,2	General Test Requisition	Serum	1.0 ml serum	Collect blood in serum separator tubes (SST)
Histoplasma Serology^1,2	General Test Requisition	Serum	1.0 ml serum	Collect blood in serum separator tubes (SST)
Blastomyces Serology^1,2	General Test Requisition	Serum	1.0 ml serum	Collect blood in serum separator tubes (SST)
Coccidioides Serology^1,2	General Test Requisition	Serum	1.0 ml serum	Collect blood in serum separator tubes (SST)

Submission and Collection Notes

Complete all fields of the requisition form, including:

Test(s) requests (indicate the specific fungus/fungi being requested) and indications for testing.
Patient setting/population/source
Travel history to endemic area (if requesting Coccidioides serology)
Symptoms
Onset date

For clinical specimens, label the specimen container(s) with the patient’s first and last name, date of collection, and one other unique identifier such as the patient’s date of birth or Health Card Number. For additional information see: Criteria for Acceptance of Patient Specimens. Failure to provide this information may result in rejection or testing delay.

The specific fungal test(s) must be clearly indicated on the requisition. Requests submitted only as ‘fungal serology’ will be cancelled.

Timing of Specimen Collection

An acute serum (collected early after the onset of symptoms) and a convalescent (collected 2–3 weeks later) may be required for laboratory diagnosis.

Limitations

Haemolysed, icteric, lipemic or microbially contaminated sera or plasma are not recommended for testing.

Storage and Transport

Centrifuge serum if using SST.

Samples should be stored at 2–8°C following collection and shipped on ice packs to PHO as soon as possible. For transportation, place specimen in biohazard bag and seal.

All clinical specimens must be shipped in accordance to the Transportation of Dangerous Good Act.

Requisitions and Kit Ordering

Test Frequency and Turnaround Time (TAT)

Aspergillus EIA is performed biweekly.
TAT for Aspergillus is up to 14 business days after receipt at test site.

Histoplasma, Blastomyces and Coccidioides testing is performed once per week.
TAT for Histoplasma, Blastomyces and Coccidioides serology is up to 10 business days after receipt.

Test Methods

Aspergillus serology is tested by Enzyme Immunoassay (EIA) and detects IgG antibodies.

Histoplasma serologyis tested by Immunodiffusion and detects M and H band precipitins.

Blastomyces serology is tested by Immunodiffusion and detects A band precipitins.

Coccidioides serology is screened by EIA which detects IgM (against TP antigens) and IgG (against CF antigens). Results will be reported as “Non-Reactive”, “Indeterminate” or “Reactive”. Samples which are reactive for IgG or IgM will be further tested by Immunodiffusion.

Coccidioides is confirmed by Immunodiffusion and detects ID-TP and ID-CF band precipitins.

Limitations:
For all of these fungi, a negative result does not rule out the possibility of current infection or previous exposure.

Interpretation

The following table provides possible test results with associated interpretations:

Aspergillus IgG EIA

Result	Interpretation	Comments
Non-Reactive	No detectable level of antibody against Aspergillus	A Non-Reactive result cannot exclude the possibility of aspergillosis
Indeterminate	*Aspergillus* antibody status inconclusive. Resubmit if clinically indicated.
Reactive	Detectable level of antibody against Aspergillus	Results to be interpreted in the context of the clinical history, signs, and symptoms of the patient.

Blastomyces dermatitidis Immunodiffusion

Result	Interpretation	Comments
Non-Reactive A Band	No detectable level of antibody against Blastomyces dermatitidis	A negative test does not exclude a diagnosis of blastomycosis. If blastomycosis is suspected submit a new specimen for repeat serology or submit appropriate specimens for culture.
Partial A Band	*Blastomyces dermatitidis* antibody status inconclusive. Resubmit if clinically indicated.
Reactive A Band	Serologic evidence of infection.

Blastomyces dermatitidis serology results are reported as “Non-Reactive”, “Partial” or “Reactive”. Reactive results will indicate presence of A band (precipitins). The A band may be reported as partial band which is an indeterminate result. Reactive A band provides presumptive evidence of infection.

Histoplasma capsulatum Immunodiffusion

Scenario	M Band Result	H Band Result	Interpretation	Comments
1.	Non-Reactive	Non-reactive	*No detectable level of antibody against Histoplasma capsulatum.*	A Non-Reactive result does not exclude a diagnosis of histoplasmosis. If histoplasmosis is suspected, submit a new specimen for repeat serology or submit appropriate specimens for culture.
2.	Partial	Partial	*Histoplasma capsulatum* antibody status inconclusive. Resubmit if clinically indicated.
3.	Partial	Non-reactive	*Histoplasma capsulatum* antibody status inconclusive. Resubmit if clinically indicated.
4.	Non-reactive	Partial	*Histoplasma capsulatum* antibody status inconclusive. Resubmit if clinically indicated.
5.	Reactive	Non-reactive	Serologic evidence of infection.	Results to be interpreted in the context of the clinical history, signs, and symptoms of the patient.
6.	Reactive	Partial	Serologic evidence of infection.	Results to be interpreted in the context of the clinical history, signs, and symptoms of the patient.
7.	Non-reactive	Reactive	Serologic evidence of infection.	Results to be interpreted in the context of the clinical history, signs, and symptoms of the patient.
8.	Partial	Reactive	Serologic evidence of infection.	Results to be interpreted in the context of the clinical history, signs, and symptoms of the patient.
9.	Reactive	Reactive	Serologic evidence of acute or recent infection.

Histoplasma capsulatum serology results are reported as “Non-Reactive”, “Partial” or “Reactive”. Reactive results will indicate presence of M or H bands (precipitins), or both M and H bands. M band is indicative of recent/acute infection, as well as those who have recently recovered from histoplasmosis. H bands appear later and less frequently than M bands, and rarely in the absence of M bands. Bands may be reported as partial which is an indeterminate result.

Coccidioides immitis EIA and Immunodiffusion

Scenario	EIA Result		Immunodiffusion Result		Interpretation (for referenced comments see below)
Scenario	IgM	IgG	TP Band	CF Band	Interpretation (for referenced comments see below)
1	Non-Reactive	Non-Reactive	Not done	Not done	No detectable level of antibody against Coccidioides immitis¹
2.	Indeterminate	Indeterminate	Not done	Not done	Coccidioides immitis antibody status inconclusive.²
3.	Indeterminate	Non-Reactive	Not done	Not done	Coccidioides immitis antibody status inconclusive.²
4.	Non-Reactive	Indeterminate	Not done	Not done	Coccidioides immitis antibody status inconclusive.²
5.	Reactive	Reactive	Reactive	Reactive	Serologic evidence of acute or recent infection.
6.	Reactive	Reactive	Reactive	Non-Reactive	Serologic evidence of acute or recent infection.
7.	Reactive	Reactive	Partial	Reactive	Serologic evidence of infection.³
8.	Reactive	Reactive	Non-Reactive	Non-Reactive	Coccidioides immitis antibody status inconclusive.²
9.	Reactive	Reactive	Reactive	Partial	Serologic evidence of acute or recent infection.
10.	Reactive	Reactive	Partial	Partial	Coccidioides immitis antibody status inconclusive.²
11.	Reactive	Reactive	Non-Reactive	Partial	Coccidioides immitis antibody status inconclusive.²
12.	Reactive	Reactive	Partial	Non-Reactive	Coccidioides immitis antibody status inconclusive.²
13.	Reactive	Indeterminate	Reactive	Reactive	Serologic evidence of acute or recent infection.
14.	Reactive	Indeterminate	Reactive	Non-Reactive	Serologic evidence of acute or recent infection.
15.	Reactive	Indeterminate	Non-Reactive	Reactive	Serologic evidence of infection.³
16.	Reactive	Indeterminate	Non-Reactive	Non-Reactive	Coccidioides immitis antibody status inconclusive.²
17.	Reactive	Indeterminate	Reactive	Partial	Serologic evidence of acute or recent infection.
18.	Reactive	Indeterminate	Partial	Reactive	Serologic evidence of infection.³
19.	Reactive	Indeterminate	Partial	Partial	Coccidioides immitis antibody status inconclusive.²
20.	Reactive	Indeterminate	Non-Reactive	Partial	Coccidioides immitis antibody status inconclusive.²
21.	Reactive	Indeterminate	Partial	Non-Reactive	Coccidioides immitis antibody status inconclusive.²
22.	Reactive	Non-Reactive	Reactive	Reactive	Serologic evidence of acute or recent infection.
23.	Reactive	Non-Reactive	Reactive	Non-Reactive	Serologic evidence of acute or recent infection.
24.	Reactive	Non-Reactive	Non-Reactive	Reactive	Serologic evidence of infection.
25.	Reactive	Non-Reactive	Non-Reactive	Non-Reactive	Coccidioides immitis antibody status inconclusive.2
26.	Reactive	Non-Reactive	Reactive	Partial	Serologic evidence of acute or recent infection.
27.	Reactive	Non-Reactive	Partial	Reactive	Serologic evidence of infection.
28.	Reactive	Non-Reactive	Partial	Partial	Coccidioides immitis antibody status inconclusive.²
29.	Reactive	Non-Reactive	Non-Reactive	Partial	Coccidioides immitis antibody status inconclusive.²
30.	Reactive	Non-Reactive	Partial	Non-Reactive	Coccidioides immitis antibody status inconclusive.²
31.	Indeterminate	Reactive	Reactive	Reactive	Serologic evidence of acute or recent infection.
32.	Indeterminate	Reactive	Reactive	Non-Reactive	Serologic evidence of acute or recent infection.
33.	Indeterminate	Reactive	Non-Reactive	Reactive	Serologic evidence of recent, past or chronic infection.
34.	Indeterminate	Reactive	Non-Reactive	Non-Reactive	Coccidioides immitis antibody status inconclusive.²
35.	Indeterminate	Reactive	Reactive	Partial	Serologic evidence of infection.
36.	Indeterminate	Reactive	Partial	Reactive	Serologic evidence of recent, past or chronic infection.
37.	Indeterminate	Reactive	Partial	Partial	Coccidioides immitis antibody status inconclusive.²
38.	Indeterminate	Reactive	Non-Reactive	Partial	Coccidioides immitis antibody status inconclusive.²
39.	Indeterminate	Reactive	Partial	Non-Reactive	Coccidioides immitis antibody status inconclusive.²
40.	Non-Reactive	Reactive	Reactive	Reactive	Serologic evidence of acute or recent infection.
41.	Non-Reactive	Reactive	Reactive	Non-Reactive	Serologic evidence of infection.
42.	Non-Reactive	Reactive	Non-Reactive	Reactive	Serologic evidence of recent, past or chronic infection.
43.	Non-Reactive	Reactive	Non-Reactive	Non-Reactive	Coccidioides immitis antibody status inconclusive.²
44	Non-Reactive	Reactive	Reactive	Partial	Serologic evidence of infection.
45.	Non-Reactive	Reactive	Partial	Reactive	Serologic evidence of recent, past or chronic infection.
46.	Non-Reactive	Reactive	Partial	Partial	Coccidioides immitis antibody status inconclusive.²
47.	Non-Reactive	Reactive	Non-Reactive	Partial	Coccidioides immitis antibody status inconclusive.²
48.	Non-Reactive	Reactive	Partial	Non-Reactive	Coccidioides immitis antibody status inconclusive.²

Coccidioides Interpretation Comments:

A non-reactive serologic test result does not rule out the possibility of current infection. If coccidiomycosis is suspected resubmit a new specimen for repeat serology or submit appropriate specimens for culture.
An inconclusive serologic test result does not rule out the possibility of infection. If coccidiomycosis is suspected resubmit a new specimen for repeat serology or submit appropriate specimens for culture.
Advise follow-up specimen for repeat serology if clinically indicated.

Coccidioides immitis Immunodiffusion results are reported for both ID-TP and ID-CF bands (precipitins) as “Non-Reactive”, “Partial” or “Reactive”. Formation of ID-TP bands is evidence of acute or recent infection. Formation of ID-CF bands is evidence of recent past or chronic Coccidioides infection. ID-TP and ID-CF bands may be reported as partial bands; this should be interpreted as an inconclusive result.

Reporting

Results are reported to the physician, authorized health care provider (General O. Reg 45/22, s.18) or submitter as indicated on the requisition.