Positive "alveolar" responses to antigen inhalation provocation tests: their validity and recognition

Area of Science:

• Pulmonary Medicine
• Immunology
• Occupational Health

Background:

• Extrinsic allergic alveolitis (EAA) diagnosis relies on identifying hypersensitivity to inhaled antigens.
• Inhalation challenge tests are used to investigate EAA but require careful assessment of validity and safety.

Purpose of the Study:

• To assess the validity and reliability of inhalation tests in diagnosing extrinsic allergic alveolitis.
• To identify objective monitoring measurements that reliably confirm positive inhalation test responses.

Main Methods:

• 144 antigen and control inhalation tests were performed on 31 subjects with suspected EAA.
• Subjects included bird fancier's lung, farmer's lung, and mushroom worker's lung.
• Objective measurements monitored included exercise minute ventilation, body temperature, neutrophil and lymphocyte counts, and forced vital capacity.

Main Results:

• A definitive pattern of positive late responses was observed in EAA subjects.
• Positive tests were associated with influenza-like symptoms and significant changes in six objective measurements (exercise ventilation, temperature, neutrophils, respiratory rate, lymphocytes, FVC).
• These confirmatory tests demonstrated high specificity (approx. 95%) and good sensitivity (85-48%).

Conclusions:

• Inhalation tests are valid for diagnosing EAA, with specific objective measures confirming positive reactions.
• Less sensitive tests like diffusing capacity, lung volumes, resting ventilation, auscultation, and chest radiography are not sufficiently useful.
• Inducing significant changes in insensitive tests is deemed unnecessarily distressing and potentially hazardous.