What is being tested?
Albumin is a protein that is present in large amounts in the blood. When kidneys are functioning properly, only a tiny amount of albumin leaks through into the urine, less than 30 mg/day. In kidney failure (the last stage of a slow process of decline in kidney function), large amounts of protein are spilled into the urine. A long time before this amount of damage happens, small changes in the kidney allow very small but abnormal amounts of albumin to leak through, usually as a result of having diabetes. This condition is called microalbuminuria and the test that measures this very small amount of albumin is called albumin/creatinine ratio urine (ACRU).
How is the test used?
Urine microalbumin is used to screen those at risk of developing Chronic Kidney Disease, even very small increases in albumin may indicate impaired kidney health. 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 microalbuminuria 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 or prevented.
Microalbumin is also a marker for cardiovascular disease for type 2 diabetics.
When is it requested?
ACRU should be requested when a person is first diagnosed with diabetes to establish a baseline level. After that, screening is usually annual using the ACRU test. When significant levels of albumin have been found, the test may be done more frequently.
What does the result mean?
Moderately increased ACRU levels in urine indicate that a person is in one of the very early phases of developing kidney disease. Recently, studies have shown that an abnormal ACRU result indicates an increased risk of developing heart and blood vessel (cardiovascular) complications, especially in people with diabetes. Low levels are an indication that kidney function is normal.
Moderate to high, persistently elevated levels of albumin in urine over three to six months is a requirement for establishing a diagnosis.
Other causes of elevation of albumin in urine which tend to be transient are fever, infection, exercise, high blood pressure and raised lipid levels.
Is there anything else I should know?
ACRU should be performed on the first specimen of urine passed after getting up in the morning. If this is not possible a random urine specimen is acceptable.
Note vigorous exercise is a common cause of transient elevation of urine albumin, and should not be performed for 24 hours prior to collecting the urine sample.
Similarly acute febrile illness and urinary infection may cause transient elevations so it is preferable sample be taken when patient is well.
There are dipsticks available for urine albumin measurement, but they may be subject to false positive or negative results depending on the urine volume for the sample tested.
Albumin to Creatinine Ratios Urine (ACRU) for moderate excretion range from 3.4 to 34 mg/mmol of Creatinine, and is associated with declining kidney function.
ACRU ratios higher than 34mg/mmol are indicative of markedly increased levels of albumin in urine and have a high predictive value of renal disease progression.
The serum prealbumin test is only used infrequently and measures a protein that reflects your nutritional status. It is sometimes done before and after surgery, or if you are taking nutritional supplements. Albumin testing is used more frequently, often to test for liver or kidney disease. Albumin can also be used to monitor nutritional status. However, prealbumin changes more quickly, making it more useful for detecting changes in short-term nutritional status than albumin. The UACR test measures very small levels of albumin in your urine and may indicate whether you are at risk for developing kidney disease.
UACR tests for a small amount of albumin, not smaller molecules. If you are diabetic, each year your doctor will test a sample of your urine to see if your kidneys are leaking albumin, even in small amounts. It is good news if your kidneys are not leaking even small amounts of albumin. This means your kidneys are working well.
Yes, albuminuria is not specific for diabetes. It may also be associated with hypertension (high blood pressure), some lipid abnormalities and several immune disorders. Moderately increased levels are also associated with cardiovascular disease risk.
Temporary elevated results may also be caused by vigorous exercise, blood in the urine, urinary tract infection, fever, dehydration and some drugs.
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