Urine Albumin to Creatinine Ratio or ACR
At a Glance
Why Get Tested?
To be screened for the early detection of kidney disease occurring as a complication of diabetes or hypertension (high blood pressure)
When to Get Tested?
Annually after a diagnosis of diabetes or hypertension
Sample Required?
A urine sample
The Test Sample
What is being tested?
Albumin is a protein that is present in large amounts in the blood. When kidneys are working properly, only tiny amounts of albumin leak through 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, usually as a result of having diabetes. Too little albumin is present to be detected by the usual simple urinalysis with a test strip or dipstick method. (It used to called “microalbumin” because of its low concentration, not because it is a smaller molecule).
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 will be measured by a sensitive method and related to the creatinine concentration and reported as an albumin/creatinine ratio or ACR. The ACR has been shown to be of greater diagnostic value than the measurement of albumin alone in timed urine samples, largely because of difficulties in making accurately timed urine collections.
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.
The Test
How is it used?
Diabetes is a very common cause of kidney failure. Studies have shown that identifying diabetics in the very early stages of kidney disease by demonstrating an abnormal ACR helps patients and doctors adjust treatment. With better diabetic control and better control of other complications, such as high blood pressure, the progression of diabetic kidney disease can be slowed down or prevented.
When is it requested?
ACR should be requested when diabetes is first diagnosed. It is then usually measured annually. If significantly raised ACR values are found the test may be done more frequently.
What does the test result mean?
A moderately increased ACR indicates an early phase of developing kidney disease. Very high values show that kidney disease is present in a more severe form. Normally very low values show that kidney function is normal.
Is there anything else I should know?
Recently, studies have shown that in patients with Type II diabetes, an abnormal ACR result indicates an increased risk of developing heart and blood vessel complications.
Common Questions
Ask a Laboratory Scientist
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.
