Classification systems for hypersensitivity pneumonitis

Classical classification	Boyd classification	Cormier classification	Selman classification	Vasakova classification
Acute	Acute progressive	Active	Active nonprogressive and intermittent	Acute: Symptom duration <6 months*; mostly reversible
Subacute	Acute intermittent nonprogressive	Active	Acute progressive and intermittent	Acute: Symptom duration <6 months*; mostly reversible
Chronic	Nonacute	Residual	Chronic	Chronic-fibrotic: symptom duration >6 months*; may be partially reversible, but risk of progression
			Nonprogressive
			Progressive
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; 84:839.	Boyd G, McSharry CP, Banham SW, Lynch PP. A current view of pigeon fancier's lung. A model for pulmonary extrinsic allergic alveolitis. Clin Allergy 1982; 12 Suppl:53.	Cormier, Y, Lacasse, Y. Keys to the diagnosis of hypersensitivity pneumonitis: The role of serum precipitins, lung biopsy, and high-resolution computed tomography. Clin Pulm Med 1996; 3:72.	Interstitial Lung Disease, Schwarz MI, King TE Jr, (Eds), 5th ed, Shelton, CT, People's Medical Publishing House, 2011.	Vasakova M, Morell F, Walsh S, et al. Hypersensitivity Pneumonitis: Perspectives in Diagnosis and Management. Am J Respir Crit Care Med 2017; 196:680.

* Approximate duration.

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