Microalbuminuria

What is being measured?
The microalbumin test is an early indicator of kidney failure. It measures the small amounts of albumin that the body starts to release into the urine several years before significant kidney damage becomes apparent. Albumin is a protein produced in the liver. It is present in high concentrations in the blood, but when the kidneys are working properly virtually no albumin is allowed to pass into the urine. If a person’s kidneys are damaged or diseased, however, they start to lose their ability to filter proteins. This is often seen in chronic diseases such as diabetes and high blood pressure, with increasing protein in the urine reflecting increasing kidney failure.

Since the albumin molecule is small, it is one of the first proteins to be detected in the urine when there is kidney damage. Patients who have persistently detectable amounts of albumin in their urine (microalbuminuria) are at increased risk of developing kidney failure and cardiovascular disease in the future. Microalbumin can be measured using urine samples collected over 24 hours, over a set period (for example 4 hours or overnight), or at random (spot)

Creatinine is a product of muscle metabolism and is normally excreted in the urine at a steady rate. Its level in urine is therefore relatively stable. Since the concentration (or dilution) of urine varies during the day, this property of creatinine means that creatinine can be used as a correction factor for random urine samples. When creatinine is measured together with microalbumin on a random urine sample, the result is expressed as the microalbumin/creatinine ratio (also called ACR). This test is recommended by the American Diabetes Association as the reference test for screening for microalbuminuria.

How is the sample collected for testing?
You will be asked to collect a random urine sample while you are at the doctor’s surgery or laboratory, or a timed urine sample (for example every four hours or overnight), or you may be asked to collect all your urine over 24 hours. Your doctor or the laboratory will give you the containers and instructions for collecting the sample properly.

Is any preparation needed to ensure the quality of the sample?
No preparation is needed

1. How is it used?
2. When is it requested?
3. What does the result mean?
4. Is there anything else I should know?

1. How is it used?
Random microalbumin or the microalbumin/creatinine ratio is often requested as a screening test in patients with chronic diseases, such as diabetes and high blood pressure, which in themselves increase the risk of developing kidney failure. Studies have shown that identifying the very early stages of kidney disease (microalbuminuria) helps patients and doctors manage treatment. With better control of diabetes and high blood pressure, through tight blood glucose control and lower blood pressure, the progression of diabetic kidney disease can be slowed or even prevented.

A timed microalbumin test (4 hours or overnight) may be requested as an alternative screening tool. If significant amounts of microalbumin are found with these screening tests, they should then be confirmed with a 24-hour urine microalbumin test.

2. When is it requested?
In the USA the National Kidney Foundation recommends that everyone with diabetes aged between 12 and 70 have a urine test for microalbuminuria at least once a year. According to the American Diabetes Association, everyone with type 1 diabetes should be tested every year starting five years after diagnosis, and everyone with type 2 diabetes should start at the time of diagnosis. If microalbuminuria is found, it should be confirmed with a second test, and if it is positive in two out of three measurements over 3-6 months, it is considered present and the patient should start appropriate treatment.

Patients with high blood pressure should be tested at regular intervals, as often as their doctor recommends.

3. What does the result mean?
Moderately raised levels of microalbumin in the urine indicate that a person is at a very early stage of developing kidney disease. Very high levels indicate that kidney disease is present in a more severe form. Normal levels indicate that kidney function is normal.

4. Is there anything else I should know?
Studies have shown that raised urine albumin levels in people with diabetes or high blood pressure are associated with an increased risk of developing cardiovascular disease (CVD), even when these levels are within the reference ranges. More recently, research has focused on whether raised urine albumin levels indicate cardiovascular risk in people who do not have diabetes or high blood pressure.

1. What is the difference between the albumin, prealbumin and microalbumin tests?
2. Is microalbumin just a smaller albumin molecule?
3. What does this test look for in my urine?
4. Are there other reasons for raised microalbumin in the urine?

1. What is the difference between the albumin, prealbumin and microalbumin tests?
The prealbumin test measures a protein that reflects a person’s nutritional status, particularly before and after surgery, in hospital or when taking nutritional supplements. The albumin test is most often used to check for liver or kidney disease or to find out whether the body is not absorbing enough amino acids. Albumin can also be used to monitor nutritional status. However, prealbumin changes more quickly, which makes it more useful than albumin for detecting short-term changes in nutritional status. The microalbumin test measures very small amounts of albumin in the urine and can show whether you are at risk of developing kidney disease.

2. Is microalbumin just a smaller albumin molecule?
No; the microalbumin test measures small amounts of albumin, not smaller molecules.

3. What does this test look for in my urine?
If you have diabetes, every year your doctor will have a sample of your urine tested to see whether your kidneys are releasing albumin, even in small amounts. It is good news if your kidneys are not releasing even small amounts of albumin.

4. Are there other reasons for raised microalbumin in the urine?
Yes, microalbuminuria is not specific to diabetes. It can also be associated with hypertension (high blood pressure), some lipid disorders and various immune system disorders. High levels can also be caused by intense exercise, blood in the urine, urinary tract infections, dehydration and some medicines.