Medscape is available in 5 Language Editions – Choose your Edition here.


Farmer's Lung Workup

  • Author: Laurianne G Wild, MD, FAAAAI, FACAAI; Chief Editor: Zab Mosenifar, MD, FACP, FCCP  more...
Updated: Dec 21, 2015

Laboratory Studies

No single diagnostic or clinical laboratory study is specific to the diagnosis of farmer's lung. The most important diagnostic tool is a detailed environmental history. Note the following:

  • Leukocytosis with neutrophilia (but not eosinophilia) and elevated erythrocyte sedimentation rate (ESR), C-reactive protein level, and quantitative immunoglobulin level are noted.
  • Precipitating immunoglobulin G (IgG) antibodies confirms past exposure but does not indicate active disease.
  • Precipitating antibodies are present in up to 50% of asymptomatic farmers exposed to the antigen. [14]
  • In farmer's lung, negative precipitin results have been reported because of a lack of appropriate antigen selection in serologic commercial testing.
  • Laboratories must select antigens based on knowledge of local climate and agricultural practices rather than reliance on commercially available antigen panels.

Imaging Studies

Chest radiography

Findings are normal between acute attacks. Findings are abnormal during acute and subacute stages of disease.

Diffuse air-space consolidation is typical of acute farmer's lung (with acute antigen exposure). Nodular or reticulonodular pattern is characteristic of the subacute phase. Linear radiodensities may be discovered and indicate areas of fibrosis from previous attacks.

Pulmonary apices are often spared on plain chest radiography.

High-resolution computed tomography

High resolution CT scanning is a superior diagnostic modality compared with plain radiography. A normal finding on high-resolution CT scans eliminates the possibility of active acute or chronic farmer's lung.

Pulmonary fibrosis with honeycombing is observed in chronic disease. Peri-bronchovascular distribution of nodules with ground-glass attenuation may be observed.



Other Tests

Pulmonary function tests

Spirometry findings may be normal between attacks and before the development of chronic disease. Acute, subacute, and chronic forms of farmer's lung have a restrictive ventilatory pattern with reduced forced vital capacity (FVC), reduced total lung capacity (TLC), and preserved airflow.

Mild-to-severe hypoxemia at rest or during minimal exercise may be present with active disease. Decreased diffusion capacity is present with active disease.




  • Bronchoscopy is useful to exclude other disease processes in the acute setting and to obtain bronchoalveolar lavage (BAL) fluid samples for cell counts.
  • Transbronchial biopsy may show evidence of peri-bronchovascular granuloma formation supporting the diagnosis, but its yield is limited because of sampling size.

Open lung biopsy

  • Consider this procedure if noninvasive tests are equivocal or inconclusive.
  • Consider this procedure if the patient's presentation is atypical in the presence of significant clinical evidence for the disease.

Histologic Findings

Chronic interstitial inflammation is present with infiltration of plasma cells, mast cells, histiocytes, and lymphocytes. Small and poorly organized nonnecrotizing granulomas are present, usually adjacent to bronchioles. Interstitial fibrosis is often present in chronic disease. Changes consistent with bronchiolitis obliterans may be evident. Guidelines for diagnosis of farmer's lung are as follows:

  • Major criteria
    • Symptoms compatible with hypersensitivity pneumonitis
    • Evidence of exposure to appropriate antigen by history or detection of antigen-specific antibody in serum and/or BAL fluid
    • Characteristic radiographic changes on plain radiographs or high-resolution CT scans
    • Bronchoalveolar lymphocytes (if BAL was performed)
    • Pulmonary histological changes compatible with hypersensitivity pneumonitis (if lung biopsy was performed)
    • Positive natural challenge findings (reproduction of symptoms and laboratory abnormalities after exposure to the probable environment)
  • Minor criteria
    • Presence of bibasilar rales
    • Decreased diffusion capacity
    • Arterial hypoxemia either at rest or during exercise
Contributor Information and Disclosures

Laurianne G Wild, MD, FAAAAI, FACAAI Chief and Professor of Clinical Medicine, Section of Clinical Immunology, Allergy and Rheumatology, Director, Allergy and Immunology Fellowship Training Program, Tulane University School of Medicine; Director, Allergy and Immunology Clinic, Southeast Louisiana Veterans Health Care System of New Orleans

Laurianne G Wild, MD, FAAAAI, FACAAI is a member of the following medical societies: Alpha Omega Alpha, American Academy of Allergy Asthma and Immunology, American College of Allergy, Asthma and Immunology, Association of Subspecialty Professors

Disclosure: Nothing to disclose.


Eduardo E Chang, MD Fellow, Department of Allergy and Immunology, Tulane University

Disclosure: Nothing to disclose.

Specialty Editor Board

Francisco Talavera, PharmD, PhD Adjunct Assistant Professor, University of Nebraska Medical Center College of Pharmacy; Editor-in-Chief, Medscape Drug Reference

Disclosure: Received salary from Medscape for employment. for: Medscape.

Chief Editor

Zab Mosenifar, MD, FACP, FCCP Geri and Richard Brawerman Chair in Pulmonary and Critical Care Medicine, Professor and Executive Vice Chairman, Department of Medicine, Medical Director, Women's Guild Lung Institute, Cedars Sinai Medical Center, University of California, Los Angeles, David Geffen School of Medicine

Zab Mosenifar, MD, FACP, FCCP is a member of the following medical societies: American College of Chest Physicians, American College of Physicians, American Federation for Medical Research, American Thoracic Society

Disclosure: Nothing to disclose.

Additional Contributors

Sat Sharma, MD, FRCPC Professor and Head, Division of Pulmonary Medicine, Department of Internal Medicine, University of Manitoba; Site Director, Respiratory Medicine, St Boniface General Hospital

Sat Sharma, MD, FRCPC is a member of the following medical societies: American Academy of Sleep Medicine, American College of Chest Physicians, American College of Physicians-American Society of Internal Medicine, American Thoracic Society, Canadian Medical Association, Royal College of Physicians and Surgeons of Canada, Royal Society of Medicine, Society of Critical Care Medicine, World Medical Association

Disclosure: Nothing to disclose.


Gregg T Anders, DO Medical Director, Great Plains Regional Medical Command , Brooke Army Medical Center; Clinical Associate Professor, Department of Internal Medicine, Division of Pulmonary Disease, University of Texas Health Science Center at San Antonio

Disclosure: Nothing to disclose.

  1. Ramazzini B, Wright WC, eds. De Morbis Artificium [Diseases of Workers]. New York, NY: Hafner Publishing; 1964.

  2. Barrera C, Valot B, Rognon B, Zaugg C, Monod M, Millon L. Draft genome sequence of the principal etiological agent of farmer's lung disease, Saccharopolyspora rectivirgula. Genome Announc. 2014 Dec 18. 2(6):[Medline]. [Full Text].

  3. Lehrer SB, Turer E, Weill H, Salvaggio JE. Elimination of bagassosis in Louisiana paper manufacturing plant workers. Clin Allergy. 1978 Jan. 8(1):15-20. [Medline].

  4. Liu S, Chen D, Fu S, et al. Prevalence and risk factors for farmer's lung in greenhouse farmers: an epidemiological study of 5,880 farmers from Northeast China. Cell Biochem Biophys. 2015 Mar. 71(2):1051-7. [Medline].

  5. Barrera C, Millon L, Rognon B, et al. Immunoreactive proteins of Saccharopolyspora rectivirgula for farmer's lung serodiagnosis. Proteomics Clin Appl. 2014 Dec. 8(11-12):971-81. [Medline].

  6. Ashitani J, Kyoraku Y, Yanagi S, Matsumoto N, Nakazato M. Elevated levels of beta-D-glucan in bronchoalveolar lavage fluid in patients with farmer's lung in Miyazaki, Japan. Respiration. 2008. 75(2):182-8. [Medline].

  7. Deschenes D, Provencher S, Cormier Y. Farmer's lung-induced hypersensitivity pneumonitis complicated by shock. Respir Care. 2012 Mar. 57(3):464-6. [Medline].

  8. Bellanger AP, Reboux G, Botterel F, et al. New evidence of the involvement of Lichtheimia corymbifera in farmer's lung disease. Med Mycol. 2010 Nov. 48(7):981-7. [Medline].

  9. Hanak V, Golbin JM, Ryu JH. Causes and presenting features in 85 consecutive patients with hypersensitivity pneumonitis. Mayo Clin Proc. 2007 Jul. 82(7):812-6. [Medline].

  10. Depierre A, Dalphin JC, Pernet D, et al. Epidemiological study of farmer's lung in five districts of the French Doubs province. Thorax. 1988 Jun. 43(6):429-35. [Medline]. [Full Text].

  11. Malmberg P, Rask-Andersen A, Palmgren U, Hoglund S, Kolmodin-Hedman B, Stalenheim G. Exposure to microorganisms, febrile and airway-obstructive symptoms, immune status and lung function of Swedish farmers. Scand J Work Environ Health. 1985 Aug. 11(4):287-93. [Medline].

  12. Kokkarinen J, Tukiainen H, Terho EO. Mortality due to farmer's lung in Finland. Chest. 1994 Aug. 106(2):509-12. [Medline].

  13. Arya A, Roychoudhury K, Bredin CP. Farmer's lung is now in decline. Ir Med J. 2006 Jul-Aug. 99(7):203-5. [Medline].

  14. Cormier Y, Belanger J. The fluctuant nature of precipitating antibodies in dairy farmers. Thorax. 1989 Jun. 44(6):469-73. [Medline].

  15. Arshad M, Braun SR, Sunderrajan EV. Severe hypoxemia in farmer's lung disease with normal findings on chest roentgenogram. Chest. 1987 Feb. 91(2):274-5. [Medline].

  16. Monkare S, Ikonen M, Haahtela T. Radiologic findings in farmer's lung. Prognosis and correlation to lung function. Chest. 1985 Apr. 87(4):460-6. [Medline].

  17. Cormier Y, Brown M, Worthy S, Racine G, Muller NL. High-resolution computed tomographic characteristics in acute farmer's lung and in its follow-up. Eur Respir J. 2000 Jul. 16(1):56-60. [Medline].

  18. Roussel S, Reboux G, Dalphin JC, Laplante JJ, Piarroux R. Evaluation of salting as a hay preservative against farmer's lung disease agents. Ann Agric Environ Med. 2005. 12(2):217-21. [Medline].

  19. Barbee RA, Callies Q, Dickie HA, Rankin J. The long-term prognosis in farmer's lung. Am Rev Respir Dis. 1968 Feb. 97(2):223-31. [Medline].

  20. Ohtsuka Y, Munakata M, Tanimura K, et al. Smoking promotes insidious and chronic farmer's lung disease, and deteriorates the clinical outcome. Intern Med. 1995 Oct. 34(10):966-71. [Medline].

  21. Thorshauge H, Fallesen I, Ostergaard PA. Farmer's lung in infants and small children. Allergy. 1989 Feb. 44(2):152-5. [Medline].

  22. Lacasse Y, Fraser RS, Fournier M, Cormier Y. Diagnostic accuracy of transbronchial biopsy in acute farmer's lung disease. Chest. 1997 Dec. 112(6):1459-65. [Medline].

  23. Takahashi T, Munakata M, Ohtsuka Y, et al. Serum KL-6 concentrations in dairy farmers. Chest. 2000 Aug. 118(2):445-50. [Medline].

  24. Nakagawa-Yoshida K, Ando M, Etches RI, Dosman JA. Fatal cases of farmer's lung in a Canadian family. Probable new antigens, Penicillium brevicompactum and P olivicolor. Chest. 1997 Jan. 111(1):245-8. [Medline].

  25. Imai K, Ashitani J, Imazu Y, et al. [Farmer's lung cases of a farmer and his son with high BAL fluid beta-D glucan levels]. Nihon Kokyuki Gakkai Zasshi. 2004 Dec. 42(12):1024-9. [Medline].

  26. Ando M, Suga M. Hypersensitivity pneumonitis. Curr Opin Pulm Med. 1997 Sep. 3(5):391-5. [Medline].

  27. Bouchard S, Morin F, Bedard G, Gauthier J, Paradis J, Cormier Y. Farmer's lung and variables related to the decision to quit farming. Am J Respir Crit Care Med. 1995 Sep. 152(3):997-1002. [Medline].

  28. Cormier Y, Belanger J. Long-term physiologic outcome after acute farmer's lung. Chest. 1985 Jun. 87(6):796-800. [Medline].

  29. Emanuel DA, Kryda MJ. Farmer's lung disease. Clin Rev Allergy. 1983 Dec. 1(4):509-32. [Medline].

  30. Fink JN, Zacharisen MC. Hypersensitivity pneumonitis. Middleton E Jr, Reed CE, Ellis EF, Adkinson NF Jr, Yunginger JW, Busse WW, eds. Allergy Principles and Practice. 5th ed. St. Louis, Mo: Mosby; 1998. 994-1004.

  31. Fink JN. Hypersensitivity pneumonitis. Clin Chest Med. 1992 Jun. 13(2):303-9. [Medline].

  32. Fraser RG, Pare JA. Diagnosis of Diseases of the Chest. 3rd ed. Philadelphia, Pa: WB Saunders; 1989. 1273-90.

  33. Gay J, Donham KJ, Leonard S. Iowa Agricultural Health and Safety Service Project. Am J Ind Med. 1990. 18(4):385-9. [Medline].

  34. Kaltreider HB. Hypersensitivity pneumonitis. West J Med. 1993 Nov. 159(5):570-8. [Medline].

  35. Kline JN, Schwartz DA. Agricultural dust-induced lung disease. Rom WN, ed. Environmental Occupational Medicine. Philadelphia, Pa: Lippincott Raven; 1998. 565-71.

  36. Kokkarinen JI, Tukiainen HO, Terho EO. Recovery of pulmonary function in farmer's lung. A five-year follow-up study. Am Rev Respir Dis. 1993 Apr. 147(4):793-6. [Medline].

  37. Lalancette M, Carrier G, Laviolette M, et al. Farmer's lung. Long-term outcome and lack of predictive value of bronchoalveolar lavage fibrosing factors. Am Rev Respir Dis. 1993 Jul. 148(1):216-21. [Medline].

  38. Myers ML. Health problems and disease patterns in agriculture. Encyclopedia of Occupational Health Safety. Geneva, Switzerland: International Labour Office; 1997.

  39. Patel AM, Ryu JH, Reed CE. Hypersensitivity pneumonitis: current concepts and future questions. J Allergy Clin Immunol. 2001 Nov. 108(5):661-70. [Medline].

  40. Patterson R, Greenberger PA, Castile RG, et al. Diagnostic problems in hypersensitivity lung disease. Allergy Proc. 1989 Mar-Apr. 10(2):141-7. [Medline].

  41. Salvaggio JE. Extrinsic allergic alveolitis (hypersensitivity pneumonitis): past, present and future. Clin Exp Allergy. 1997 May. 27 Suppl 1:18-25. [Medline].

  42. Schuyler M, Cormier Y. The diagnosis of hypersensitivity pneumonitis. Chest. 1997 Mar. 111(3):534-6. [Medline].

  43. Schuyler M, Gott K, Edwards B. Experimental hypersensitivity pneumonitis: cellular requirements. Clin Exp Immunol. 1996 Jul. 105(1):169-75. [Medline].

  44. Wiatr E, Radzikowska E, Pawlowski J. [Pulmonary fibrosis in young patients with hypersensitivity pneumonitis]. Pneumonol Alergol Pol. 2004. 72(3-4):111-6. [Medline].

  45. Wild LG. Hypersensitivity pneumonitis: A childhood disease?. Pediatr Asth Allergy. 2000. 14:57-75.

  46. Wild LG, Lopez M. Hypersensitivity pneumonitis: a comprehensive review. J Investig Allergol Clin Immunol. 2001. 11(1):3-15. [Medline].

  47. Rognon B, Reboux G, Roussel S, et al. Western blotting as a tool for the serodiagnosis of farmer's lung disease: validation with Lichtheimia corymbifera protein extracts. J Med Microbiol. 2015 Apr. 64(Pt 4):359-68. [Medline].

All material on this website is protected by copyright, Copyright © 1994-2016 by WebMD LLC. This website also contains material copyrighted by 3rd parties.