In which clinical scenarios is relying on the urine protein-to-creatinine ratio as a measure of proteinuria unreliable, and interpretations should be made looking at urine protein and urine creatinine separately?  

I typically only use spot UPCRs because (1) they are easy to obtain and thus trend (2) they account for BSA indirectly because it accounts for Cr excretion. The best role of urine protein measurements is really just to trend if your therapy is effective or to screen for disease. When looking at urin...