Microalbumin and
Microalbumin/Creatinine Ratio
At a Glance
Why Get Tested?
To get screened for a possible kidney disorder or for early damage to the kidneys in those with diabetes
When to Get Tested?
Annually after a diagnosis of diabetes or hypertension
Sample Required?
Test Preparation Needed?
None
The Test Sample
What is being tested?
The microalbumin test is an early indicator of kidney failure. It measures the tiny amounts of albumin that the body begins to release into the urine several years before significant kidney damage becomes apparent. Albumin is a protein that is produced in the liver. It is present in high concentrations in the blood, but when the kidneys are functioning properly, virtually no albumin is allowed to leak through into the urine. If a person’s kidneys become damaged or diseased, however, they begin to lose their ability to filter proteins out of the urine. This is frequently seen in chronic diseases, such as diabetes and hypertension, with increasing amounts of protein in the urine reflecting increasing kidney failure.
Since the albumin molecule is small, it is one of the first proteins to be detected in the urine with kidney damage. Patients who have consistently detectible amounts of albumin in their urine (microalbuminuria) have an increased risk of developing progressive kidney failure and cardiovascular disease in the future. Microalbumin measurements can be obtained using urine collected over a 24-hour period, for a specified amount of time (e.g., 4 hours or overnight), or randomly (spot).
Creatinine, a byproduct of muscle metabolism, is normally excreted into the urine on a consistent basis. Its level in the urine is relatively stable. Since the concentration (or dilution) of urine varies throughout the day, this property of creatinine allows its measurement to be used as a corrective factor in random/spot urine samples. When a creatinine measurement is performed along with a random microalbumin, the result is the microalbumin/creatinine ratio (also called the albumin/creatinine ratio (ACR)), which the American Diabetes Association states is the preferred test for screening for microalbuminuria.
How is the sample collected for testing?
You will be asked to collect either a random sample of urine while you are at the doctor's office or laboratory, a timed urine sample (such as 4 hours or overnight), or you may be requested to collect a complete 24-hour urine sample. Your doctor or the laboratory will give you a container and instructions for properly collecting a timed or 24-hour urine sample.
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?
The random microalbumin test or microalbumin/creatinine ratio is frequently ordered as a screening test on patients with chronic conditions, such as diabetes and hypertension, that put them at an increased risk of developing kidney failure. Studies have shown that identifying the very early stages of kidney disease (microalbuminuria) helps patients and doctors adjust treatment. With better control of diabetes and hypertension by maintaining tight glycemic control and reducing blood pressure, the progression of diabetic kidney disease can be slowed or prevented.
A timed microalbumin test (4 hour or overnight) may be ordered as an alternative screening tool. If significant amounts of microalbumin are detected with these screening tests, they may be confirmed with a 24-hour microalbumin test.
When is it ordered?
The National Kidney Foundation recommends that everyone with diabetes between 12 and 70 years of age have a urine test for microalbuminuria at least once a year. According to the American Diabetes Association, everyone with type 1 diabetes should get tested annually, starting 5 years after onset, and all those with type 2 diabetes should start at the time of diagnosis. If microalbuminuria is detected, it should be confirmed by retesting and, if positive on 2 of 3 determinations over a 3-6 month period, it is considered to be present and appropriate treatment should be given.
Patients with hypertension may be tested at regular intervals, with the frequency determined by their doctor.
What does the test result mean?
Moderately increased microalbumin levels in urine indicate that a person is in one of the very early phases of developing kidney disease. Very high levels are an indication that kidney disease is present in a more severe form. Normal levels are an indication that kidney function is normal.
Is there anything else I should know?
Studies have shown that elevated levels of urinary albumin in people with diabetes or hypertension are associated with increased risk of developing cardiovascular disease (CVD), even if those levels are within the normal reference range. More recently, research has been focused on trying to determine if increased levels of albumin in the urine are also indicative of CVD risk in those who do not have diabetes or high blood pressure.
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 in Current Review
National Kidney Foundation. Fact Sheet: Microalbuminuria In Diabetic Kidney Disease. Available online at http://www.kidney.org/news/newsroom/fs_new/microalbindbkd.cfm through http://www.kidney.org. Accessed December 2008.
MedlinePlus Medical Encyclopedia. Microalbuminuria test. Available online at http://www.nlm.nih.gov/MEDLINEPLUS/ency/article/003591.htm. Accessed December 2008.
US FDA. Diabetes Information, Glucose Meters & Diabetes Management. Available online at http://www.fda.gov/Diabetes/glucose.html#22. Accessed December 2008.
American Diabetes Association. Clinical Practice Recommendations 2008. Diabetes Care. January 2008, Volume 31, Supplement 1. Available online at http://care.diabetesjournals.org/content/vol31/Supplement_1/. Accessed December 2008.
Wang TJ, Gona P, Larson G, et al. Multiple biomarkers for the prediction of first major cardiovascular events and death. New England Journal of Medicine. 21 Dec 2006. 355;25:2631-2639.
High Levels Of Urinary Albumin In The Normal Range Predict Hypertension. ScienceDaily (June 25, 2008). Available online at http://www.sciencedaily.com/releases/2008/06/080625123002.htm through http://www.sciencedaily.com. Accessed December 2008.
Holly Kramer et al. Urine Albumin Excretion and Subclinical Cardiovascular Disease. Hypertension. 2005;46:38. Available online at http://hyper.ahajournals.org/cgi/content/abstract/46/1/38. Accessed December 2008.
Sources Used in Previous Reviews
Corbett, JV. Laboratory Tests & Diagnostic Procedures with Nursing Diagnoses, 4th ed. Stamford, Conn.: Appleton & Lang, 1996. Pp. 73-74.
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.
Nuovo, J. (1999 June). Albumin-to-Creatinine Ratio for Detection of Microalbuminuria. American Family Physician, Tips from other Journals [On-line journal]. Available online at http://www.aafp.org/afp/990600ap/tips.html#31 through http://www.aafp.org.
Fitz, M. (1999 February 2). Spot Urine Albumin to Creatinine Ratio. Loyola University Chicago Stritch School of Medicine. [On-line information, Medicine 1]. Available online at http://www.meddean.luc.edu/Lumen/meded/MEDICINE/medclerk/renal13.htm through http://www.meddean.luc.edu.
Ehrmeyer, S. (2003 January). Using a creatinine ratio in urinalysis to improve the reliability of protein and albumin results. Medical Laboratory Observer, Features 35 (1) [On-line journal]. Available online at http://www.mlo-online.com/articles/mlo0103cliniss.htm through http://www.mlo-online.com.
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.
Virtual Hospital: University of Iowa Family Practice Handbook, 3rd Edition: Hematologic, Electrolyte, and Metabolic Disorders: Bibliography. Available online at http://www.vh.org/Providers/ClinRef/FPHandbook/Chapter05/Bibliography05.html through http://www.vh.org
ARUP Laboratory Guidebook. Available online at http://www.arpulab.com/guides/clt/ through http://www.arpulab.com. (Click on “microalbumin, urine”)
American Diabetes Association: Community and Resources. Available online at http://www.diabetes.org.
