What criteria do you use to decide when to perform a BAL in hypersensitivity pneumonitis?  

Short answer: When the vibes are right. I know that's a flippant answer, but that's an honest-to-God real answer. Long answer: This is really complicated and personally, I'm frustrated by our guidelines and the level of evidence we have for diagnosing HP. To answer the question, it's worth...

Short answer(s):1) Almost all cases of suspected acute/non-fibrotic HP. There is a differential to consider in most of these patients including infectious causes, and the benefit of ruling out infection and establishing a diagnosis (since BAL lymphocyte % is typically quite elevated i.e. >40% in ...