Hypersensitivity Pneumonitis IgG Antibodies, Serum
Clinical Information Discusses physiology, pathophysiology, and general clinical aspects, as they relate to a laboratory test
Hypersensitivity pneumonitis (HP) is a heterogeneous disease caused by exposure to organic dust antigens, animal proteins, chemicals, medications, or microorganisms (eg, Thermoactinomyces vulgaris, Micropolyspora faeni, Aspergillus fumigatus). The immunopathogenesis of disease is not known; but, several immunologic mechanisms may play a role in producing alveolitis, including cellular immunity mediated by CD4 and CD8 T-lymphocytes, immune-complex mediated inflammation, complement activation or activation of alveolar macrophages.(1)
HP is suspected clinically in patients who present with intermittent or progressive pulmonary symptoms and interstitial lung disease. The diagnosis is established by compatible clinical and radiographic findings, pulmonary function tests, and demonstration of specific antibodies to organic antigens known to cause the disease.
Evaluation of patients suspected of having hypersensitivity pneumonitis induced by exposure to Aspergillus fumigatus, Thermoactinomyces vulgaris, or Micropolyspora faeni
Elevated concentrations of IgG antibodies to Aspergillus fumigatus, Thermoactinomyces vulgaris, or Micropolyspora faeni in patients with signs and symptoms of hypersensitivity pneumonitis is consistent with disease caused by exposure to 1 or more of these organic antigens. Extreme elevations (>5 times the upper limit of normal) occur in some patients with active disease.(2)
Cautions Discusses conditions that may cause diagnostic confusion, including improper specimen collection and handling, inappropriate test selection, and interfering substances
IgG antibodies to Aspergillus fumigatus, Thermoactinomyces vulgaris, or Micropolyspora faeni are detectable in sera from healthy individuals and the presence of antibodies is not sufficient to establish the diagnosis of hypersensitivity pneumonitis (HP).
Elevated concentration of antibodies to Aspergillus fumigatus are found in patients with invasive aspergillosis and cavitary lung disease as well as HP.(2)
The levels of antibodies to these antigens often decrease following treatment; but elevated levels may persist in treated patients for long periods.
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.
Aspergillus fumigatus, IgG ANTIBODIES
<4 years: not established
> or =4 years: < or =102 mg/L
Micropolyspora faeni, IgG ANTIBODIES
0-12 years: < or =4.9 mg/L
13-18 years: < or =9.1 mg/L
>18 years: < or =13.2 mg/L
Thermoactinomyces vulgaris, IgG ANTIBODIES
0-12 years: < or =6.6 mg/L
13-18 years: < or =11.0 mg/L
>18 years: < or =23.9 mg/L
Clinical References Provides recommendations for further in-depth reading of a clinical nature
1. Fink JN, Zacharisen MC: Hypersentivity pneumonitis. In Allergy Principles and Practice. Vol. 1. Fifth edition. Edited by E Middleton, Jr., CE Reed, EF Ellis, et al. St. Louis, MO, Mosby Year Book, Inc., 1998, Chapter 69
2. Anderson E, Jacob GL, Robert GD, Homburger HA: Comparative evaluation of enzyme immunoassay and immunodiffusion for detection of IgG antibodies to hypersensitivity pneumonitis antigens. Poster Presentation, AAAAI Annual Meeting, San Diego, CA, March 3-8, 2000. J Allergy Clin Immunol 2000;105:S304