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Confirm the presence of precipitating antibodies to Thermoactinomyces sacchari.
A positive test does not establish the diagnosis of hypersensitivity pneumonitis, nor does the absence of precipitins eliminate the diagnosis.
Hypersensitivity pneumonitis (HP), also referred to as extrinsic allergic alveolitis (EAA), is an inflammatory lung disease resulting from the inhalation and subsequent sensitization to a wide variety of inhaled organic dusts.1-5 Exposure to Thermoactinomyces sacchari can result from contact with moldy sugar cane causing a condition referred to as malt worker's lung or bagassosis1-3 HP is not mediated by IgE. It is associated with progressive pulmonary disability, irreversible lung damage, and mortality in some occupational settings.1-5 Patients often present with intermittent chills, fever, cough, and shortness of breath that begin four to eight hours after exposure to the offending dust.
No single laboratory test is diagnostic for hypersensitivity pneumonitis.1-5 Diagnosis is based on a complete environmental history supported by result of chest x-ray, spirometry, and in vitro immunologic tests.1-5 Identification of the causative agent is important to allow avoidance of exposure.2,5 Double diffusion (Ouchterlony) assays are typically used to determine antigen-specific IgG antibodies.5 The appearance of precipitin arcs confirms the presence of precipitating antibodies to specific antigens. These antibodies may also be present in individuals not afflicted with HP.2,3,5 The presence of antibodies to the offending dust or antigen confirms exposure but is not diagnostic of HP; however, upon repeated or prolonged exposures, high levels of precipitating IgG antibodies are typically observed.
1. Richerson HB, Bernstein IL, Fink JN, et al. Guidelines for the clinical evaluation of hypersensitivity pneumonitis. Report of the Subcommittee on Hypersensitivity Pneumonitis. J Allergy Clin Immunol. 1989 Nov; 84(5 Pt 2):839-844. PubMed 2809034
2. Patel AM, Ryu JH, Reed CE. Hypersensitivity pneumonitis: Current concepts and future questions. J Allergy Clin Immunol. 2001 Nov; 108(5):661-670. PubMed 11692086
3. Kurup VP, Fink JN. Immunological tests for evaluation of hypersensitivity pneumonitis an allergic bronchopulmonary aspergillosis. In Rose NR, Hamilton RG, Detrick B, eds.Manual of Clinical Laboratory Immunology. 6th ed. Washington, DC: ASM Press;2002:910-919.
4. Zacharisen MC, Fink JN. Hypersensitivity pneumonitis. In Grammar LC, Greenberger PA, eds. Patterson's Allergic Disease. 6th ed. Philadelphia, Pa: Lippincott Williams and Wilkins; 2002:515-528.
5. Greer Laboratories Inc. Hypersensitivity Pneumonitis/Extrinsic Allergic Alveolitis. Technical Bulletin #47. Lenoir, NC: Greer; 2004. Yi ES. Hypersensitivity pneumonitis. Crit Rev Clin Lab Sci. 2002 Nov; 39(6):581-629. PubMed 12484500
