Positive 'alveolar' responses to antigen inhalation provocation tests: Their validity and recognition

Abstract

The validity of inhalation tests in the investigation of extrinsic allergic alveolitis was assessed from the results of 144 antigen and control tests in 31 subjects. A definitive pattern of positive late responses was observed. Reactions to nebulized bird serum and droppings in subjects with bird fancier's lung were identical to reactions after 'natural' exposures in aviaries or lofts, and to reactions after 'occupational' challenges in subjects with farmer's lung and mushroom worker's lung. In general, positive tests were easily recognized subjectively from symptoms and signs appropriate to an influenza-like illness and undue respiratory effort on exercise. They were associated with significant changes in 6 readily available objective monitoring measurements - exercise minute ventilation ( ≥ + 15%), body temperature (>37.2°C), circulating neutrophils (≥ + 2500/mm3), exercise respiratory frequency (≥ + 25%), circulating lymphocytes (≥ -500/mm3 with lymphopenia), and forced vital capacity (≥ -15%). These confirmatory monitoring tests had specificities of approximately 95% and sensitivities of 85-48%. Measurement of diffusing capacity, lung volume subdivisions, or resting minute ventilation/respiratory frequency proved to be too insensitive to be useful, as did auscultation and chest radiography. The authors conclude that responses that do provoke significant changes in these less sensitive tests are unnecessarily distressing and, presumably, unnecessarily hazardous.