Would you treat a patient aggressively for lupus nephritis if they have persistent proteinuria over 1 gram but cannot get a timely kidney biopsy?

It all depends.

1. I would keep pushing for a biopsy and try to overcome the barriers ASAP. If it is the patient who is the barrier (not wanting the biopsy), I would educate them on how a biopsy ends up not even being due to SLE in some cases and immunosuppressant treatment therapy would be exposing them to inappropriate therapy with unneeded potential side effects. If we do the biopsy, and it is ISN/RPS class I or II, I would not treat it differently than I would usually treat their lupus (other than use ACEi/ARB etc). If antiphospholipid nephropathy is seen, then I'd recommend warfarin therapy. About 1% of the time, we'll see podocytopathy, for which steroids and ACEi/ARBs usually do the trick (usually do not need stronger immunosuppressant...

Insufficient information to provide a response with confidence as the first order of operations is to determine, as best as possible, if LN patient with persistent proteinuria has active disease (i.e., ongoing immune complex-mediated injury) for which alternative or additional immunosuppression is warranted versus the entity of fixed or sclerotic proteinuria (e.g., even absent ongoing immune injury prior glomeruli with damaged slit diaphragms and effacement of epithelial podocyte foot process yet not fully sclerotic will have blood flow that is permissive for proteinuria) in which case additional anti-proteinuric therapy may be indicated. Variables to take into account include the following: original ISN/RPS class as well as NIH AI and CI, ...

I presume the patient has established SLE and isolated proteinuria. If that is the case, the patient will need a biopsy. In extreme scenarios where biopsy is impossible to obtain, treatment will be based as Dr. @Dr. First Last mentions on the specifics of the case.