Normally functioning kidneys remove waste products from the blood, while ensuring important substances such as albumin stay in the blood.
Albumin is required in the body to help prevent water leaking from the blood into other tissues. When kidneys become damaged, they may start to leak albumin from the blood into the urine.
An excess level of albumin in the urine is referred to as albuminuria. When a person has a slightly increased level of urine albumin (30 to 300mg albumin per 24 hours), the term “microalbuminuria” is used. When the level is more than 300mg of albumin per 24 hours, it is termed as “macroalbuminuria”.
Persistent albuminuria indicates that the kidney is malfunctioning. Persistent albuminuria is confirmed when a person’s urine tests positive for albumin over a period of several weeks. This is one of the first signs of diabetic kidney disease.
Other conditions that can cause albuminuria include hypertension, kidney damage from nephrotic syndrome, congestive heart failure, and the metabolic syndrome.
Around eight percent of adults have microalbuminuria and one percent have macroalbuminuria.
Among people with diabetes, the incidence of albuminuria is one in three and for those with hypertension, it is one in seven. It also affects one in every six people older than 60 years.
Testing for Albuminuria
Albuminuria can be tested in a random sample of urine using different methods. The protein can be quickly detected using dipstick testing, which involves dipping a strip of paper into a urine sample.
If the dipstick test is negative, a more accurate test may be performed which measures the ratio of albumin to creatinine present in blood.
This test is found to give precise results when a random early morning urine sample is used, but sometimes a sample collected over a 24 hour period is used.
When a random single urine sample is used, a positive result is indicated by more than 30mg of albumin per gram of creatinine, while for a 24- hour collection, about 30 to 300mg of albumin indicates albuminuria.
When is Testing Required?
Anyone who has type 1 or type 2 diabetes and is aged between 12 and 70 years should have their urine checked for the presence of albumin every year.
It is recommended that individuals with risk factors for chronic kidney disease such as hypertension or a family history of kidney failure are also regularly tested for albuminuria.
A positive result should be confirmed using a second test.
Kidney Disease
Kidney disease is a serious condition, where the filtering structures in the kidney, referred to as glomeruli, become so scarred that they can no longer effectively filter the blood.
Over time, kidney failure may develop, in which case, dialysis or even a kidney transplant may be required for a person to survive.
Problems Other than Kidney Disease
As well as kidney disease, a positive test for albuminuria suggests an increased risk for heart disease among individuals with or without diabetes or another long-term illness.
Further Reading
Presidential advisory by the American Heart Association: connecting cardiovascular, kidney, and metabolic health