Protein is not normally found in the urine, and urine protein tests detect and/or measure protein being excreted in the urine. Urine protein tests are useful to evaluate and monitor kidney function as well as to detect early kidney damage.
Proteinuria is frequently seen in chronic diseases (such as diabetes or hypertension) with increasing amounts of protein in the urine reflecting increased kidney damage. Excess protein production, such as may be seen with multiple myeloma, can also lead to proteinuria.
Urine protein tests can be performed in a random or 24-hour urine samples. A semi-quantitative test such as dipstick urine protein is a screening performed as a part of routine urinalysis. A positive dipstick protein may be elevated due to other sources of protein, such as blood, semen, or vaginal secretions in the urine. Since it measures primarily albumin, it may occasionally be normal when significant quantities of other proteins are present in the urine (globulins, immunoglobulins).
Additional tests such as urine protein electrophoresis can be performed to determine exactly what proteins are being excreted and in what quantities.