Urine Protein and Urine Protein to Creatinine Ratio

Why Get Tested?
To detect excessive protein escaping into the urine, to help evaluate and monitor kidney function, and to detect kidney damage
When to Get Tested?
As part of a routine physical, as a follow-up to a previous positive urine protein test, or when you have a disorder or disease that affects the kidney
Sample Required?
A random or 24-hour urine sample; occasionally, a split 24-hour sample, with the night collection separated from the day collection.
How is it used?
Urine protein testing is used to detect protein in the urine, to help evaluate and monitor kidney function, and to help detect and diagnose early kidney damage and disease. A semi-quanititative test such as a dipstick urine protein is used to screen the general population for the presence of protein in the urine as part of a routine urinalysis. If slight to moderate amounts of protein are detected, then a repeat urinalysis and dipstick protein may be performed at a later time to see if there is still protein in the urine or if it has dropped 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 a 24-hour urine protein may be used as a follow-up test. Since the dipstick primarily measures albumin, the 24-hour urine protein test also may be ordered 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 are present or the cause of the proteinuria. When a doctor is investigating the reason, he also may order a serum and urine protein 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 order a Comprehensive Metabolic Panel (CMP) 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 may also may imaging scans to evaluate the appearance of the organ.

A protein to creatinine ratio may be ordered on a random urine sample if a child shows evidence of significant and persistent protein in their urine with the dipstick urine test. Children, and sometimes adults, occasionally 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 used to monitor a patient with known kidney disease or damage. A dipstick urine protein and/or a protein to creatinine ratio may be used to screen patients on a regular basis when they are taking a medication that may affect their kidney function.

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