Diabetes and Lipid Clinic of Alaska

 

 

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About the Microalbuminuria Test

The microalbuminuria test is a urine test used to detect small amounts of the protein albumin in urine. It is a common screening test for kidney disease (nephropathy), a serious complication of diabetes.

Normally, little or no protein appears in the urine. As blood flows through the kidneys, waste products and extra fluid are filtered through tiny holes in the glomeruli (small blood vessels) and become urine. Useful materials, such as protein, are too large to pass through the holes and remain in the blood, where they are employed for purposes such as protecting the body against infection, building cells, aiding in blood clotting and regulating blood pressure.

Diabetes can damage this filtering system. Hyperglycemia (high blood glucose) can cause the kidneys to filter too much blood. Over time, the kidneys can begin to lose their filtering ability, resulting in kidney disease. As a result, waste products begin to build up in the blood, and useful protein and red blood cells are lost in urine. The presence of small amounts of albumin in the urine is known as microalbuminuria.

Produced by the liver, albumin is normally in the blood in high amounts. Because albumin molecules are small, they will fit through growing holes that can develop in the glomeruli. As a result, albumin is one of the first types of protein to be detected in the urine.

Microalbuminuria is an early sign of kidney disease, a common complication of diabetes. Trace amounts of albumin are released into the urine several years before kidney damage becomes evident. It is important to detect kidney disease in its early stages because doing so increases the chance of preventing or delaying its progression. If microalbuminuria is left undetected or untreated, higher levels of protein will begin to leak into the urine (proteinuria). Chronic kidney failure (endstage renal disease) may follow, along with the need for dialysis or a kidney transplant.

At its earliest stages, kidney disease has no symptoms. In fact, 80 percent of the kidney must be damaged before problems become noticeable. Therefore, it is especially important for those at risk of developing kidney disease to have their urine tested for microalbuminuria.

Factors that increase a person’s risk of kidney disease include:

  • Diabetes
  • High blood pressure
  • Age (older adults are at an increased risk)
  • Ethnicity (black Americans, Hispanic Americans, Asian Americans, Pacific Islanders and American Indians are at increased risk)
  • Weight (overweight people are at increased risk)
  • Family history of chronic kidney disease

Microalbuminuria also is a predictor of other diseases of the blood vessels, but the reason for this is unknown, according to the National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK).

The American Diabetes Association (ADA) recommends that people with type 2 diabetes be tested for microalbuminuria at the time of their diagnosis and then annually. People with type 1 diabetes should be tested five years after being diagnosed and then annually.

Some patients, however, will need to be tested more frequently. Additional microalbuminuria tests may be ordered to detect the progression of kidney disease in those diagnosed with microalbuminuria. More frequent testing may also be recommended in patients diagnosed with damage to blood vessels in other areas of the body (e.g., heart, eyes, limbs) or those taking medications that may harm the kidneys. A physician can recommend how often a patient should be tested.

It is important to note that a standard urinalysis will not detect the tiny amounts of protein present with microalbuminuria. People with diabetes or other risk factors for kidney disease should make sure they are undergoing a microalbuminuria test.

Types and Differences of Tests

The sample required for a microalbuminuria test may vary. Possible urine samples required include:

  • 24-hour urine sample. A collection of all urine voided in a 24–hour period.
  • Overnight urine sample. A collection of all urine voided between going to sleep at night and waking up in the morning.
  • Timed urine sample. A collection of all urine voided in a specific period of time (e.g., four hours).
  • Spot urine sample (also called dipstick method). A random single urine sample

Because the amount of albumin in the urine varies throughout the day, the 24– hour urine sample is the most accurate sample for microalbuminuria testing. However, collecting a 24–hour sample can be time consuming. As an alternative, a physician may also request a timed, overnight or spot sample. When abnormal amounts of albumin are detected in one of these alternative samples, a 24–hour test may be ordered to confirm the results.

Another method of microalbuminuria testing is measuring the albumin–to–creatinine ratio in a spot urine sample. Because spot urine samples are not as reliable as 24–hour urine samples, creatinine measurement can be used to increase accuracy.

Creatinine is a waste product that comes from two sources: meat products in the diet and from wear and tear on the muscles. Almost all of it eventually ends up in a person’s urine, where its level remains relatively stable, regardless of variations in concentration or dilution of the urine. As a result, creatinine measurements are considered a reliable corrective factor in spot urine samples. When creatinine levels are measured along with albumin, the resulting ratio provides information that comes close to accuracy of a 24–hour urine sample, without the inconvenience.

A spot urine sample may detect proteinuria but not the tinier molecules of protein present in microalbuminuria, according to the National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK). It recommends the other methods of checking for microalbuminuria, including the addition of creatinine testing.

Understanding MicroalbuminuriaTest Results

Normally, little or no albumin is detectable in urine. The presence of little or no albumin suggests that the patient’s kidney function is normal. Moderately increased albumin levels (microalbuminuria) may indicate that the patient is in the early stages of kidney disease. High levels of albumin may indicate that the patient has proteinuria and is in a more severe stage of kidney disease.

Microalbuminuria test results may be translated as follows:

 

Normal

Mico-albuminuria

Proteinuria

Spot sample (µg/mg* creatinine)

<30

30 to 299

> 300

24-hour sample (mg/24h*)

<30

30 to 299

>300

Time sample (µg/min*)

<20

20 to 199

>200

Overnight sample (µg/min)

<20

20 to 199

>200

*µg/mg = microgram per milligram
*mg/24 h = milligrams in 24 hours
*µg/min = micrograms per minute


However, additional testing may be required before a diagnosis is made. Because the amount of albumin in the urine can vary from day to day, the results of two out of three urine samples, collected within a three– to six–month period, should be abnormal before a patient is diagnosed with microalbuminuria.

In addition to diabetic nephropathy, other factors that can cause elevated microalbuminuria levels include:

  • High blood pressure
  • Urinary tract infection or other infection
  • Dehydration
  • Fever
  • Infection
  • Heart failure
  • Lipid abnormalities
  • Vigorous exercise within 24 hours of the test
  • Blood in the urine (hematuria)
  • Certain immune disorders (e.g., systemic lupus erythematosus)

Microalbuminuria testing may need to be avoided when one or more of these factors are present.

When microalbinuria has been confirmed, the patient’s physician will recommend treatment options. In people with diabetes, the progression of kidney disease may be slowed or prevented by improving control of glucose (blood sugar) control and reducing blood pressure, because high blood pressure can cause kidney damage.

Antihypertensive medication such as ACE inhibitors or angiotensin II receptor blockers may be prescribed, even to patients who do not have high blood pressure. Reducing the amount of protein, and other changes in diet, may also be recommended.

Additional testing will be required to track the progression of the disease. Please consult with the physicians at Diabetes and Lipid Clinic of Alaska for additional information.

The information on this Web page is provided for educational purposes. You understand and agree that this information is not intended to be, and should not be used as, a substitute for medical treatment by a health care professional. You agree that Diabetes and Lipid Clinic of Alaska is not making a diagnosis of your condition or a recommendation about the course of treatment for your particular circumstances through the use of this Web page. You agree to be solely responsible for your use of information contained on this Web page

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