What criteria do you use to determine when to start a steroid-sparing agent for hypersensitivity pneumonitis?

This is a very challenging question, acknowledging the difficulty in confidently establishing the diagnosis of HP, limited evidence in general to guide the treatment of HP, and recent small observational studies that conflict prior small observational studies.

To attempt to answer, breaking down into 2 groups, acute/non-fibrotic HP and fibrotic HP:

Acute/non-fibrotic HP - If mild, and the antigen is able to be identified and removed, I may not treat at all. First-line treatment, if needed, would be moderate dose prednisone with a taper, and I reserve using a steroid-sparing agent (almost always mycophenolate) for those intolerant of steroids due to side effects, or whose disease worsens when tapering prednisone below 10mg/day or so.

Fibrotic...