How is proteinuria diagnosed?
Proteinuria is diagnosed through a urine test. The patient provides a urine sample, which is examined in a lab. Doctors use a “dipstick” – a thin plastic stick with chemicals on the tip – to test part of the sample right away. If too much of any substance is in the urine, the chemical tip changes color.
The remainder of the urine is then examined under a microscope. Doctors look for substances that don’t belong in urine. These substances include red and white blood cells, bacteria and crystals that can grow and develop into kidney stones.
What happens when chronic kidney disease or another serious condition is diagnosed or suspected?
A doctor who suspects kidney disease would repeat the urine test three times over three months. If the samples test positive for proteins each time, the patient likely has kidney disease. The earlier the diagnosis, the more chance doctors have to slow the disease and stop it from progressing.
Additional tests might include:
- Blood test to measure the levels of creatinine (chemical waste products). Healthy kidneys move these substances from the blood to the urine. If the kidneys are not working properly, creatinine will remain in the blood.
- Blood test to estimate the glomerular filtration rate (GFR). The GFR compares a patient’s size, age, sex and race to levels of creatinine and albumin in the blood. The GFR tells a doctor how well the kidneys are working and how far the kidney disease has advanced. It also helps the doctor plan treatment.
- Blood test to measure all proteins in the serum. The serum is part of the blood filled with proteins.
- Imaging tests like CT scans and ultrasounds. These tests show images of the kidneys, helping doctors spot problems like kidney stones, tumors or obstruction of the urinary tract.
- Urine protein electrophoresis. Doctors search for specific types of proteins in a urine sample. For example, the presence of a protein called Bence-Jones might indicate multiple myeloma (cancer of plasma cells).
- Immunofixation blood test. This test finds proteins called immunoglobulins – which are antibodies that fight infection – in the blood. Too many of the same immunoglobulins can indicate blood cancer.
- A kidney biopsy. This is a procedure involving removal of a tiny piece of kidney. Doctors examine the sample under a microscope to determine what caused the kidney disease and the extent of damage.