Urine Albumin to Creatinine Ratio or ACR

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Also known as: Urine microalbumin

The Test Sample

What is being tested?

Albumin is a protein that is present in large amounts in the blood. When the kidneys are working properly, only tiny amounts of albumin pass from the bloodstream into the urine. In kidney failure (the last stage of a slow process of decline in kidney function) large amounts of protein leak into the urine. A long time before this amount of damage, small changes in the blood-filtering parts of the kidney allow very small, but abnormal amounts of albumin to leak through, often as a result of having diabetes. Too little albumin is present to be detected by the usual simple urinalysis with a test strip (sometimes called a protein dipstick). This condition used to be termed microalbuminuria because of the low but significant concentration of albumin in the urine, not because it is a smaller type of the protein; however this term has been abandoned because it can be confusing. It is now simply called albuminuria.

How is the sample collected for testing?

You will be asked to collect either an early morning or random sample of urine in which albumin and creatinine will be measured by sensitive methods. The measurements are expressed as an albumin/creatinine ratio or ACR for short. The use of this ratio allows the albumin concentration to be related to the dilution of urine (as indicated by the creatinine concentration) which can depend on how much fluid you have consumed that day. ACR measurement in random urine samples has been shown to be just as good as the measurement of albumin alone in 24 hour urine samples and is much more convenient for the person being tested.

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.