Summary

• The albumin-creatinine ratio (ACR) test is used to see how well your kidneys are working.
• It does this by measuring the level of a protein called albumin in your urine. 
• Albumin is found in large amounts in the blood.
• Your kidneys filter your blood and normally only a tiny amount of albumin leaks into your urine.
• If your kidneys are damaged, they allow too much albumin to pass through. 
• The test also measures creatinine another substance filtered by your kidneys. 
• An ACR test compares the amount of albumin to the amount of creatinine.
• This is a more accurate way to measure the amount of albumin in your urine than using albumin alone.

What is an albumin-creatinine ratio test?

Albumin is a protein that is found in large amounts in the blood. Your kidneys filter your blood and normally when they are working properly only a tiny amount of albumin leaks from your blood into your urine. Damaged kidneys let albumin pass into the urine and the more your kidneys are damaged the more albumin will be found in your urine.

Creatinine is a waste product that comes from the digestion of protein in your food and the normal breakdown of muscle tissue. It is removed from the body through the kidneys and is found in your urine.

The amount of albumin you have in your urine naturally varies throughout the day, depending on how much fluid you have recently drunk. If a single, random sample of urine were to be collected, there is no way of knowing if this is correct for the whole day. Collecting urine samples throughout a 24-hour period to assess your average levels would be inconvenient. Total daily creatinine levels are relatively consistent and by comparing the amount of albumin to creatinine it is possible to correct for the variation in urine levels.

The urine ACR test is used to screen for kidney disease. Even very small increases in albumin can indicate that your kidneys aren’t working well. By detecting very small amounts of albumin in your urine, this test can pick up early kidney damage. Increased amounts of albumin in the urine are known as albuminuria.

Why get tested?

People who have diabetes, high blood pressure, heart disease, certain autoimmune disorders or a family history of kidney failure are at risk of kidney disease.

In kidney failure, large amounts of protein spill into the urine. A long time before this amount of damage happens, small changes in the kidneys allow very small amounts of albumin to leak into the urine. When this occurs, it is called microalbuminuria. The ACR test can measure these small amounts of albumin, and it is used to screen people at risk of developing chronic kidney disease.

How your kidneys work

The kidneys are a pair of bean-shaped organs located at the bottom of the rib cage on either side of the spine.   Within them are about a million tiny blood filtering units called nephrons. In each nephron blood is continually filtered through a microscopic cluster of looping blood vessels, called the glomerulus.

The glomerulus allows the passage of water and small molecules but retains blood cells and larger molecules. Attached to each glomerulus is a tiny tube (tubule) that collects the fluid and molecules that pass through the glomerulus and then reabsorbs what still can be used by the body. The remaining waste forms urine.

Kidneys can be damaged by a range of health problems. When your kidneys are damaged waste products and fluid are less easily filtered and removed and then build up in your body.

Diabetes is a very common cause of kidney failure. Studies have shown that for people with diabetes who are in the very early stages of kidney disease, ACR testing can be helpful in adjusting treatment. With better diabetic control and better control of other issues, such as high blood pressure, the progression of diabetic kidney disease can be slowed or prevented.

The urine ACR test is most often used when someone has been diagnosed with diabetes. It can help establish a baseline level of urine albumin so that kidney function can be monitored over time to see how it responds to treatment. The test is usually done about once a year but if the albumin levels rise suddenly or by a large amount, it may be done more often. A urine albumin level that stays the same or goes down means that treatments are working.

Having the test

Sample

The urine ACR test should be performed on the first sample of urine passed after getting up in the morning. If this is not possible, a random urine specimen is acceptable. A diagnosis of albuminuria is made if two out of three ACR results show high levels.

Any preparation?

Urine albumin levels can also be temporarily raised by conditions such as high blood pressure, fever, urinary tract infection, high dietary protein, congestive heart failure, intensive exercise within 24 hours, menstruation, genital discharge or infection and some drugs.

If you have recently done any intensive exercise you should wait for 24 hours before collecting a urine sample. Similarly, if you have an illness with a high temperature or a urinary tract infection it is best that you wait until you are well before giving a sample.

Your results

Reading your test report

Your results will be presented along with any other tests your doctor ordered on the same form. You will see separate columns or lines for each of these tests.

You may see many numbers from this test on your lab report – focus on the result that has the word ratio in the name.

Your urine ACR test results help describe the degree of albuminuria you may have. A lower number is better. 

What can your results tell you?

• Low levels show that kidney function is normal if other kidney test results are normal.
• A moderately increased ACR indicates an early phase of developing kidney disease.

Moderate to high and persistently high levels of urine albumin over at least three months is needed to make a diagnosis of kidney damage.

The urine ACR test often needs to be repeated to confirm the results. Decisions are rarely made based on the results from one sample. It is usual that two out of three urine ACR test results are high, for the diagnosis of albuminuria to be confirmed.

Reference Intervals

The results of each component will be compared to reference intervals (sometimes called a normal range).

• Reference intervals are the range of results expected in healthy people. 
• If your result is outside this range, it can be flagged as high (H) or low (L) if they sit outside this range.
• Many reference intervals vary between labs so only those that are the same across most laboratories are given on this website.

If your results are flagged as high or low this does not necessarily mean that anything is wrong. It depends on your personal situation and your results need to be interpreted by your doctor.

Questions to ask your doctor

The choice of tests your doctor makes will be based on your medical history and symptoms. It is important that you tell them everything you think might help.

You play a central role in making sure your test results are accurate. Do everything you can to make sure the information you provide is correct and follow instructions closely.

Talk to your doctor about any medications you are taking. Find out if you need to fast or stop any particular foods or supplements, as these may affect your results. Ask:

• Why does this test need to be done?
• Do I need to prepare (such as fast or avoid medications) for the sample collection?
• Will an abnormal result mean I need further tests?
• How could it change the course of my care?
• What will happen next, after the test?

More information

Pathology and diagnostic imaging reports can be added to your My Health Record.

You and your healthcare provider can now access your results whenever and wherever needed. Get further trustworthy health information and advice from healthdirect.