Classification of hypersensitivity pneumonitis: A hypothesis

Yves Lacasse, Moises Selman, Ulrich Costabel, Jean Charles Dalphin, Ferran Morell, Riitta Erkinjuntti-Pekkanen, Nestor L. Mueller, Thomas V. Colby, Mark Schuyler, Valérie Jomphe, Yvon Cormier

Research output: Contribution to journalArticlepeer-review

122 Scopus citations


Background: Regardless of the causative antigen, hypersensitivity pneumonitis (HP) is usually classified as 'acute', 'subacute' or 'chronic'. Considerable confusion still surrounds this classification because there are no widely accepted criteria to distinguish the various stages. The objective of this study wasto determine whether the current classification of HP truly reflects categories of patients with distinct clinical features. Methods: Data obtained from a large prospective multicenter cohort study (the HP Study) were used to divide a cohort of patients with HP into a limited number of categories (clusters) with maximally differing clinical patterns, without prejudgment. The results of this cluster analysis were compared with the current classification of HP (acute, subacute or chronic). Results: 168 patients were included in the analysis. A 2-cluster solution best fitted the data. Patients in cluster 1 (41 patients) had more recurrent systemic symptoms (chills and body aches) and normal chest radiographs than those in cluster 2 (127 patients) who showed significantly more clubbing, hypoxemia, restrictive patterns on pulmonary function tests and fibrosis on high-resolution computed tomography (HRCT). All p values were <0.0001, using Fisher's exact test. Nodular opacities were seen on HRCT as often in cluster 1 as in cluster 2. There was considerable disagreement between the current classification of HP and the results of our analysis. Conclusion: The current classification of acute, subacute and chronic HP is not supported by our analysis. Subacute HP is particularly difficult to define.

Original languageEnglish (US)
Pages (from-to)161-166
Number of pages6
JournalInternational archives of allergy and immunology
Issue number2
StatePublished - May 2009


  • Cluster analysis
  • Extrinsic allergic alveolitis
  • Hypersensitivity
  • Pneumonitis, classification

ASJC Scopus subject areas

  • Immunology and Allergy
  • Immunology


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