Urine Albumin to Creatinine Ratio (ACR)

The urine albumin to creatinine ratio (ACR) is a medical test used to assess kidney function and detect early signs of kidney damage or disease. It measures the amount of albumin, a type of protein, in relation to creatinine, a waste product, in a patient's urine.

What is Albumin?

Albumin is a protein produced by the liver that helps keep fluid in your bloodstream so it doesn't leak into other tissues. Normally, the kidneys filter waste and excess fluids from the blood while keeping proteins like albumin. However, when the kidneys are damaged, they may let some of this protein pass into the urine.

What is Creatinine?

Creatinine is a waste product that comes from the normal wear and tear on muscles of the body. The level of creatinine in urine is relatively constant and serves as a good reference point for comparing the levels of other substances, such as albumin.

How is ACR Measured?

The ACR test involves collecting a random urine sample from the patient. The sample is then sent to a laboratory where the amounts of albumin and creatinine are measured. The ratio of albumin (in milligrams) to creatinine (in grams) is calculated, usually expressed as mg/g or sometimes as mg/mmol in different countries.

Interpretation of Results

The results of an ACR test can indicate the presence and severity of kidney damage. Generally:

• Normal: Less than 30 mg/g (or less than 3 mg/mmol) indicates that the kidneys are functioning properly.
• Mildly increased: 30-300 mg/g (or 3-30 mg/mmol) may suggest early kidney damage or disease, often seen in conditions like diabetes or hypertension.
• Moderately to severely increased: More than 300 mg/g (or more than 30 mg/mmol) indicates significant kidney damage and possible chronic kidney disease (CKD), which requires medical attention and management.

Clinical Use

The ACR test is particularly useful in the early detection of diabetic nephropathy, a common complication of diabetes that can lead to kidney failure if not managed properly. It's also used for monitoring patients with known kidney disease or those at risk due to hypertension, family history of kidney disease, or other factors.

Limitations and Considerations

While the ACR is a valuable tool for assessing kidney health, its results can be influenced by various factors such as exercise, diet, and certain medications. It's also important to note that a single abnormal result should be confirmed with repeat testing due to potential variability.

Frequently Asked Questions (FAQs)

What is the Urine Albumin to Creatinine Ratio (ACR) test?
Measures kidney damage by comparing albumin and creatinine levels in urine.

Why is the ACR test performed?
To diagnose and monitor kidney disease, especially diabetic nephropathy.

How is the ACR test done?
Requires a random urine sample, which is then sent to a lab for analysis.

What does a high ACR result indicate?
Possible kidney damage or disease, such as diabetic nephropathy.

What is a normal ACR result?
Less than 3.0 mg/mmol (or 30 mg/g) for adults.

How often should the ACR test be done?
Annually for people with diabetes or those at risk of kidney disease.

Can any medications affect ACR results?
Yes, certain medications like NSAIDs and ACE inhibitors.

Are there any preparation requirements for the ACR test?
No special preparation is usually required.

What are the risks associated with the ACR test?
None, as it's a non-invasive urine test.

Can the ACR test diagnose other conditions?
No, it specifically assesses kidney function and damage.