Testing is typically performed on a 24 hour urine. It uses a more sensitive and accurate technique for quantitating albumin, such as radioimmunoassay, immunonephelometry, or accelerated immunoturbidity.
urinary albumin excretion in µg/min =
= (mg/dL albumin in 24 hour urine) * (volume of 24 hour urine in dL) / 1440
where:
• 1440 is the number of minutes in a day
Interpretation:
• Albumin excretion in the urine is usually 2-12 µg/min, with values below 20 µg/min considered normal.
• Microalbuminuria is defined as urinary albumin excretion rate of 20-200 µg/min in 2 of 3 samples collected over a 6 month period.
• Urinary albumin excretion > 200 µg/min is considered overt proteinuria.
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24 hour urine albumin in mg per 24 hours
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24 hour urine albumin in µg/min
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Interpretation
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< 30 mg per 24 hours
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< 20 µg/min
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normal
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30 – 299 mg per 24 hours
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20 – 199 µg/min
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microalbuminuria
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>= 300 mg per 24 hours
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>= 200 µg/min
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clinical albuminuria
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Limitations:
• The test may not be interpreted correctly in the presence of confounding factors, including: urinary tract infection, fever, uncontrolled hyperglycemia, uncontrolled hypertension, and congestive heart failure.
• Proper specimen collection and accurate testing are required for meaningful results.
