Urine Protein and
Urine Protein to Creatinine Ratio

Urine protein tests are used to help assess and follow the health of the kidney, and to help detect and diagnose early kidney damage and disease. A dipstick urine protein test is frequently performed as part of a urinalysis. It is used to look for the presence of protein in the urine. If slight to moderate amounts of protein are detected, then another urinalysis and dipstick protein test may be performed at a later time to see if there is still protein in the urine or if it has fallen back to undetectable levels. If there is a large amount of protein in the first sample and/or the protein persists in the second sample, then the doctor may request a further laboratory urine protein measurement as a follow-up test. Since the dipstick primarily measures albumin, the laboratory urine protein test also may be requested if a doctor suspects that proteins other than albumin are being released.

The urine protein test tells the doctor that protein is present in the urine, but it does not indicate which types of protein are present or the cause of the proteinuria. When a doctor is investigating the reason, he also may order a serum and urine electrophoresis test to determine which proteins are being excreted and in what quantities. This is especially true if he suspects abnormal protein production, such as with multiple myeloma. He may request further tests to look at albumin and total protein levels in the blood and to help evaluate kidney and liver function. If kidney disease or damage is suspected, he also may order imaging scans to evaluate the appearance of the organ.

A protein to creatinine ratio may be requested on a random urine sample if a child shows evidence of significant and persistent protein in their urine on a dipstick urine test. Children (as well as adults) sometimes have some degree of transient proteinuria without apparent kidney dysfunction and may have a higher excretion of protein into their urine during the day than at night. The doctor may monitor their urine at intervals to see if the amount of proteinuria changes over time.

Either a 24-hour urine protein or a random protein to creatinine ratio may be ordered to monitor a patient with known kidney disease and/or damage. A dipstick urine protein and/or a protein to creatinine ratio may be used to regularly screen patients when they are taking a medication that may affect their kidney function.

A dipstick urine protein test is measured whenever a urinalysis is performed. This may be done as part of a routine check-up, a pregnancy check-up, when a urinary tract infection is suspected, as part of a hospital admission, or whenever the doctor wants to evaluate kidney function. It may also be done when a previous dipstick has been positive for protein to see if the protein excretion persists.

The laboratory random or 24-hour urine protein test may be requested as a follow-up test when the dipstick test shows that there is a large quantity of protein present in the urine and/or when protein is shown to be persistently present. Since the dipstick primarily measures albumin, the doctor may request a laboratory urine protein test even when there is little protein detected on the dipstick if he suspects that there may be proteins other than albumin being released.

When a doctor is diagnosing the cause of proteinuria he also may request a urine electrophoresis test to determine exactly which proteins are being excreted and in what quantities. A serum electrophoresis also may be used to look at the proteins in the blood, especially if abnormal protein production is suspected. Other blood tests, such as a urea and creatinine, may be used to evaluate kidney function and a albumin and/or total protein may be used to look at the proteins in the blood.

A protein to creatinine ratio may be requested on a random urine sample when a child shows evidence of significant and persistent protein in their urine on a dipstick urine test. It may also be requested when a patient has known kidney disease and/or damage and the doctor wants to monitor kidney function over time. A dipstick urine protein and/or a protein to creatinine ratio on a random urine sample may be used as a screen for kidney involvement when a patient is receiving treatment that may potentially affect kidney function.

Protein in the urine is a warning sign. It may indicate kidney damage or disease or be a transient elevation due to an infection, medication, vigorous exercise or physical stress. In some people, it may be present during the day and absent at night when the patient is lying down. Leak of protein into the urine on standing which disappears on lying down (orthostatic proteinuria) is commonly seen particularly with increasing age and it carries not health risk. In pregnant women, elevated urine protein levels can be associated with pre-eclampsia.

When kidney damage is present, the amount of protein present is generally associated with the severity of damage, and increasing amounts of protein over time indicate increasing damage and decreasing kidney function. Proteinuria is associated with many diseases and conditions, including:

• Amyloidosis
• Bladder cancer
• Congestive heart failure
• Diabetes
• Drug therapies that are potentially toxic to the kidneys
• Glomerulonephritis
• Goodpasture’s syndrome
• Heavy metal poisoning
• High blood pressure (Hypertension)
• Kidney infection
• Multiple myeloma
• Polycystic kidney disease
• Systemic lupus erythematosus
• Cystitis (Urinary tract infection)

The different methods of detecting protein in the urine vary in performance. For example, 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, the dipstick occasionally may be normal when significant quantities of other proteins are present in the urine. A 24-hour urine sample gives the protein excretion rate over 24 hours. It will be accurate only if all of the urine is collected. A random laboratory protein to creatinine ratio measurement is now considered the preferred means of assessing proteinuria and is recommended in UK National Service Frameworks (NSF) and in guidelines for the identification, management and referral of Chronic Kidney Failure (CKF).