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Test ID MPSF Micropolyspora faeni, IgG Antibodies, Serum

Reporting Name

Micropolyspora faeni, IgG Ab, S

Useful For

Evaluation of patients suspected of having hypersensitivity pneumonitis (HP) induced by exposure to Micropolyspora faeni


Evaluation of patients suspected of having HP who have documented environmental exposures on farms or ranches

Specimen Type


Specimen Required


Preferred: Serum gel

Acceptable: Red top

Specimen Volume: 0.5 mL

Specimen Minimum Volume

0.3 mL

Specimen Stability Information

Specimen Type Temperature Time Special Container
Serum Refrigerated (preferred) 21 days
  Frozen  21 days

Reference Values

0-12 years: ≤4.9 mg/L

13-18 years: ≤9.1 mg/L

>18 years: ≤13.2 mg/L

Day(s) Performed

Monday through Friday

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 US Food and Drug Administration.

CPT Code Information


LOINC Code Information

Test ID Test Order Name Order LOINC Value
MPSF Micropolyspora faeni, IgG Ab, S 26948-0


Result ID Test Result Name Result LOINC Value
MPSF Micropolyspora faeni, IgG Ab, S 26948-0

Clinical Information

Hypersensitivity pneumonitis (HP) is a type of interstitial lung disease caused by an immune-mediated response to inhaled environmental antigens.(1) Patients with HP commonly display symptoms of cough, dyspnea, and midinspiratory squeaks. Patients may present with an acute onset of symptoms (within hours of antigen exposure) or a chronic onset (which may occur over a course of weeks to months). The nature of an individual’s disease course will be affected by several factors, including quantity of inhaled antigen, intensity/frequency of exposure, and genetic background. The epidemiology of HP is also challenging to understand, as incidence and prevalence of the disease varies with geographic areas, climate, and local customs. While the immunopathogenesis of HP is not completely understood, it is presumed to involve both type III and type IV hypersensitivity reactions, with the type III reaction characterized by the presence of IgG antibodies specific for the inciting antigen.


There are many antigens, both organic and inorganic, that have been associated with development of HP.(2) Causative organic antigens include a wide array of bacteria, mycobacteria, fungi, and animal proteins. Micropolyspora faeni is a bacteria sometimes found in moldy hay; farm or ranch workers may develop IgG antibodies against this antigen, which could lead to development of HP.


Clinical practice guidelines for HP include a diagnostic algorithm that focuses on exposure identification, imaging evaluation, and bronchoalveolar lavage/histopathology.(3) Detection of IgG antibodies specific for certain environmental antigens can help to document the causative exposure for an individual. This is critical, as an important treatment for these patients is antigen avoidance. However, IgG testing is only useful as supportive information for the diagnosis of HP; a positive result only indicates sensitization to the antigen and a negative result does not exclude the possibility that a patient with HP may be sensitized to another antigen.


Positive results for IgG antibodies to Micropolyspora faeni, in patients with signs and symptoms of hypersensitivity pneumonitis, may be consistent with sensitization to this bacteria.

Clinical Reference

1. Sforza GG, Marinou A: Hypersensitivity pneumonitis: a complex lung disease. Clin Mol Allergy. 2017 Mar 7;15(6). doi: 10.1186/s12948-017-0062-7

2. Costabel U, Miyazaki Y, Pardo A, et al: Hypersensitivity pneumonitis. Nat Rev Dis Primers. 2020 Aug 6;6(1):65. doi: 10.1038/s41572-020-0191-z

3. Raghu G, Remy-Jardin M, Ryerson CJ, et al: Diagnosis of hypersensitivity pneumonitis in adults. An Official ATS/JRS/ALAT Clinical Practice Guideline. Am J Respir Crit Care Med. 2020 Aug1;202(3):e36-e69. doi: 10.1164/rccm.202005-2032ST

Report Available

2 to 4 days

Method Name

Fluorescence Enzyme Immunoassay (FEIA)