Urine Protein and
Urine Protein to Creatinine Ratio
At a Glance
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
The Test Sample
What is being tested?
Protein is not normally found in the urine, and urine protein tests detect and/or measure protein being excreted in the urine. There are several different kinds of urine protein tests. A semi-quantitative protein “dipstick” may be performed as part of a urinalysis, generally on a random urine sample. The quantity of protein in a 24-hour urine sample will be measured and reported as the amount of protein excreted per 24 hours. Also, the amount of protein in a random urine sample may be measured along with urine creatinine and reported as the ratio of urine protein to creatinine (UPCR). Creatinine, a byproduct of muscle metabolism, is normally excreted into the urine at a constant rate. When both a urine creatinine and a random urine protein test are performed, the resulting protein/creatinine ratio approaches the accuracy of the 24-hour urine protein test. Since saving all of the urine for a 24-hour period can be cumbersome for adults and difficult for infants and children, a random urine protein to creatinine ratio is sometimes substituted for a 24-hour urine protein sample.
Albumin, a protein produced by the liver, makes up about 60% of the protein in the blood. The rest is a mixture of globulins, including immunoglobulins. Proteins are not normally found in the urine. The kidneys, two organs found in the back at the bottom of the rib cage, filter the blood, removing wastes and excreting them out of the body in the form of urine. When the kidneys are functioning normally, they retain or reabsorb filtered proteins and return them to the blood. However, if the kidneys are damaged, they become less effective at filtering, and detectible amounts of protein begin to find their way into the urine. Often, it is the smaller albumin molecules that are detected first. If the damage continues, the amount of protein in the urine increases, and globulins may also begin to be lost.
Proteinuria is frequently seen in chronic diseases, such as diabetes and hypertension, with increasing amounts of protein in the urine reflecting increasing kidney damage. With early kidney damage, the patient is often asymptomatic. As damage progresses, or if protein loss is severe, the patient may have symptoms such as edema, shortness of breath, nausea, and fatigue. Excess protein production, such as may be seen with multiple myeloma, can also lead to proteinuria.
The presence of albumin in the urine (albuminuria) has been shown to be a sensitive indicator of kidney disease in patients with diabetes and with hypertension. Therefore, in some situations the doctor may test specifically for albumin in the urine, as opposed to total urine protein (see microalbumin).
How is the sample collected for testing?
A random urine sample is collected in a clean container. For a 24-hour urine collection, all of the urine is collected for a 24-hour period. It is important that the sample be refrigerated during this time period. There should be no preservative in the container.
NOTE: If undergoing medical tests makes you or someone you care for anxious, embarrassed, or even difficult to manage, you might consider reading one or more of the following articles: Coping with Test Pain, Discomfort, and Anxiety, Tips on Blood Testing, Tips to Help Children through Their Medical Tests, and Tips to Help the Elderly through Their Medical Tests.
Another article, Follow That Sample, provides a glimpse at the collection and processing of a blood sample and throat culture.
Is any test preparation needed to ensure the quality of the sample?
No test preparation is needed.
The Test
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.
When is it ordered?
A dipstick urine protein is measured frequently as a screening test, whenever a urinalysis is performed. This may be done as part of a routine physical, a pregnancy workup, 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.
A 24-hour urine protein may be ordered as a follow-up test when the dipstick test shows that there is a large quantity of protein present in the urine or when protein is shown to be persistently present. Since the dipstick primarily measures albumin, the doctor may order a 24-hour 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 order a urine protein electrophoresis test to determine exactly which proteins are being excreted and in what quantities. A serum protein electrophoresis may also be ordered to look at the proteins in the blood, especially when abnormal protein production is suspected. Other blood tests, such as a Blood Urea Nitrogen (BUN) and creatinine, may be ordered to evaluate kidney function and an albumin and/or total protein test may be performed to look at the proteins in the blood.
A protein to creatinine ratio may be ordered on a random urine sample when a child shows evidence of significant and persistent protein in their urine with the dipstick urine test. It may also be ordered when a patient has known kidney disease 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 taking a medication that may potentially affect kidney function.
What does the test result mean?
Protein in the urine is a warning sign. It may indicate kidney damage or disease or it may be a transient elevation due to an infection, medication, vigorous exercise, or emotional or physical stress. In some people, it may be present during the day and absent at night when the patient is lying down (orthostatic proteinuria). In pregnant women, elevated urine protein levels can be associated with preeclampsia.
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
- Hypertension
- Kidney infection
- Multiple myeloma
- Polycystic kidney disease
- Systemic lupus erythematosus
- Urinary tract infection
Is there anything else I should know?
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 may occasionally 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. The protein to creatinine ratio is more of a snapshot of how much protein is in the urine at the time the sample is collected. If it is elevated, then protein is present; if it is negative, it is possible that the patient was just not excreting measurable amounts of protein at that time.
Common Questions
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Article Sources
NOTE: This article is based on research that utilizes the sources cited here as well as the collective experience of the Lab Tests Online Editorial Review Board. This article is periodically reviewed by the Editorial Board and may be updated as a result of the review. Any new sources cited will be added to the list and distinguished from the original sources used.
Sources Used for Current Review
Pagana, Kathleen D. & Pagana, Timothy J. (© 2007). Mosby’s Diagnostic and Laboratory Test Reference. 8th Edition: Mosby, Inc., Saint Louis, MO. Pp 971-978.
Clarke, W. and Dufour, D. R., Editors (2006). Contemporary Practice in Clinical Chemistry. AACC Press. Washington, DC. Pp 312-317.
Wu, A. (2006). Tietz Clinical Guide to Laboratory Tests. Fourth Edition. Saunders Elsevier. St. Louis, Missouri. Pp 916-919.
Mushnick, R. (2007 October 22, Updated). Protein – urine. MedlinePlus Medical Encyclopedia [On-line information]. Available online at http://www.nlm.nih.gov/medlineplus/ency/article/003580.htm. Accessed on 9/30/08.
Mushnick, R. (2007 October 22, Updated). 24-hour urine protein. MedlinePlus Medical Encyclopedia [On-line information]. Available online at http://www.nlm.nih.gov/medlineplus/ency/article/003622.htm. Accessed on 9/30/08.
Aggarwal, N. et. al. (2008 April 22). A Prospective Comparison of Random Urine Protein-Creatinine Ratio vs 24-hour Urine Protein in Women With Preeclampsia. Medscape J Med. 2008;10(4):98 [On-line information]. Available online at http://www.medscape.com/viewarticle/571729 through http://www.medscape.com. Accessed on 9/30/08.
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Lerma, E. and McLaughlin, K. (2007 February 5, Updated). Proteinuria. EMedicine [On-line information]. Available online at http://www.emedicine.com/med/TOPIC94.HTM through http://www.emedicine.com. Accessed on 9/30/08.
Sources Used for Previous Reviews
Thomas, Clayton L., Editor (1997). Taber’s Cyclopedic Medical Dictionary. F.A. Davis Company, Philadelphia, PA [18th Edition].
Pagana, Kathleen D. & Pagana, Timothy J. (2001). Mosby’s Diagnostic and Laboratory Test Reference 5th Edition: Mosby, Inc., Saint Louis, MO.
(2004 March 17, Updated) A.D.A.M. editorial, Agha, I., previously reviewed. Protein-urine. MedlinePlus Medical Encyclopedia [On-line information]. Available online at http://www.nlm.nih.gov/medlineplus/ency/article/003580.htm.
Brose, M, Updated (2003 May 8). Protein electrophoresis – urine. MedlinePlus Medical Encyclopedia [On-line information]. Available online at http://www.nlm.nih.gov/medlineplus/ency/article/003589.htm.
Carroll, M. and Temte, J. (2000 September 15). Proteinuria in Adults: A Diagnostic Approach. American Family Physician [On-line journal]. Available online at http://www.aafp.org/afp/20000915/1333.html through http://www.aafp.org.
Loghman-Adham, M. (1998 October 1). Evaluating Proteinuria in Children. American Family Physician [On-line journal]. Available online at http://www.aafp.org/afp/981001ap/loghman.html through http://www.aafp.org.
(2003 June) Proteinuria. Kidney and Urologic Diseases Information Clearinghouse, NIH Publication No. 03-4732 [On-line information]. Available online at http://kidney.niddk.nih.gov/kudiseases/pubs/proteinuria/ through http://kidney.niddk.nih.gov.
