It all depends. 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...

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 w...

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. @Thomas mentions on the specifics of the case.