PT - JOURNAL ARTICLE AU - E. J. Hapke AU - R. M. E. Seal AU - G. O. Thomas AU - M. Hayes AU - J. C. Meek TI - Farmer's lung AID - 10.1136/thx.23.5.451 DP - 1968 Sep 01 TA - Thorax PG - 451--468 VI - 23 IP - 5 4099 - http://thorax.bmj.com/content/23/5/451.short 4100 - http://thorax.bmj.com/content/23/5/451.full SO - Thorax1968 Sep 01; 23 AB - In assessing patients suffering from farmer's lung, the acute stage must be distinguished from the chronic stage of the disease. The conspicuous radiographic signs in the acute farmer's lung episode and the often dramatic clearing make an important contribution to the diagnosis. The radiographic changes in chronic farmer's lung are not specific and cover a wide range of appearances. Even minor nodular changes are significant. Farmer's lung, acute and chronic, is not a disease predominantly characterized by a defect in gas exchange. During the acute illness the reduction in diffusing capacity is often accompanied by a decrease in lung volumes; the pulmonary function profile of the chronic stage is variable. In only a relatively small proportion of chronic farmer's lung patients does a defect in gas exchange predominate, and in some it may be manifest only during exercise. Airway obstruction is a feature of chronic farmer's lung. In chronic farmer's lung patients discrepancies between the severity of complaints and results of pulmonary function tests are not infrequent. In some patients with considerable disability conventional pulmonary function studies may demonstrate little or no impairment of the functions measured. In patients suffering from an acute farmer's lung episode, serological tests should be positive, possibly in high titre. In the chronic stage of the disease the chance of finding positive serology in a patient diminishes with the length of time elapsed since the last acute episode. The period of serological transition appears to be the third year.