This test is most often performed when kidney disease is suspected. It may be used as a screening test.
Normally, protein is not found in urine when a routine dipstick test is performed. However, tiny amounts of protein can be detected using special methods. This is because the kidney is supposed to keep large substances like protein in the blood. Even if small amounts of protein do get through, the body normally reabsorbs them.
Some proteins will appear in the urine if the levels of protein in blood become high, even when the kidney is working properly.
If the kidney is diseased, protein will appear in the urine even if blood protein levels are normal.