<prompt> Which is best for diagnosis of Hypersensitivity pneumonitis?Chest imagingPulmonary function testingSerum precipitinsClinical prediction rule  <response>: Hypersensitivity pneumonitis: Type IV HSR Chest Imaging - normal in Hypersensitivity pneumonitis Pulmonary function testing - Obstructive pattern Clinical prediction rule- eg Farmers Lung Exposure to antigen Presence of precipitin Recurrence of symptoms 4-6 hrs Crackles on auscultation Weight loss Farmer lung:- Thermophilus actinomyces 