Detection of microalbuminuria

There are many different, fast tests available for establishing the presence of microalbuminuria. These can determine within a few minutes whether there are tiny amounts of albumin in the urine (Figure 3.1). Such tests may be performed in any doctor's surgery. If protein is detected, the result of the quick test should be confirmed by a more exact measurement of the urine albumin concentration in a laboratory analysis.

Measurement of the albumin concentration is often imprecise because it depends on the amount of urine as well as the amount of excreted albumin. For example, in people who have drunk a lot of liquid before giving a urine sample, there will be a dilution effect, such that the measured albumin concentration will be too low. To compensate for this, the albumin concentration can be compared with the amount of creatine excreted in the urine.

Table 3.2 Microalbuminuria is present at the following values

According to the time of urine collection:

(a) Collection over a fixed time, e.g. overnight 20-200ug/min

(b) Collection over 24 hours 30-300 mg/24 h

According to the rate of creatine excretion:

For women 20-300 mg/g urinary creatine

2.5-35 mg/mmol urinary creatine For men 20-200 mg/g urinary creatine

2.5-25 mg/mmol urinary creatine

Table 3.1 Albumin

concentration in

the urine

Normal range

Less than 20 mg/l :


20-200 mg/l :


More than 200 mg/l ;

The best method, however, is to calculate the rate of What you should know:

albumin excretion. For this, | N0t every caSe 0f the urine has to be collected • microalbuminuria means over a given time (24 hours or : the onset of nephropathy- W . , . , , , : A'positive'test should be overnight) and the amount of ; repeated albumin excreted is divided by the set time. The range of microalbuminuria measured using different urine collection methods and time periods is shown in Table 3.2.

It is not only diabetes-associated damage that causes the kidneys to excrete albumin. Protein may also be found in the urine during physical stress, urinary tract infection, hypertension or fever. Once these conditions are resolved, the albumin usually disappears from the urine. Therefore, to be sure that microalbuminuria truly indicates the onset of diabetic nephropathy, the test should be repeated after a gap of two to four weeks. If the test is still 'positive', it is probably a sign of the start of kidney damage.

What's more, microalbuminuria is not just a sign of nephropathy. Studies have shown that people with microalbuminuria have a much higher risk of circulatory problems or a heart attack than does the general population.

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