Urine Albumin to Creatinine Ratio or ACR
A urine sample. You will be asked to collect either an early morning or random sample of urine in which albumin and creatinine will be measured. The results 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.
Albumin is a protein that is present 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 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 urine test strip (sometimes called a protein dipstick). This is termed microalbuminuria because of the low but significant concentration of albumin in the urine, not because it is a smaller type of the protein. Microalbuminuria is usually simply called albuminuria.
How is it used?
Diabetes is a very common cause of kidney failure. Studies have shown that identifying the very early stage of kidney disease in diabetes , by demonstrating an abnormal ACR,helps treatment to be appropriately adjusted. Good control of diabetes and other conditions, such as high blood pressure, can slow down or prevent the progression of kidney disease.
When is it requested?
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. Very low values generally indicate that kidney function is normal if other tests of kidney function, e.g. the glomerular filtration rate, also show no abnormality.
Is there anything else I should know?
Are there other reasons for having an increased urine albumin/creatinine ratio?
Yes, an increased ACR is not confined to diabetes and hypertension (high blood pressure). It may also be seen with a fever, urinary tract infection, several immune disorders, dehydration, certain drugs and other conditions causing blood in the urine. Temporarily elevated results may also be caused by vigorous exercise.