Albumin is an important protein (protein) of the human body (60% of the protein in the intravascular blood system is albumin). Under normal circumstances, this small, negatively charged protein (molecular weight: 66,000) is filtered out by the glomerules (renal corpuscles) and is therefore undetectable or detectable in very small amounts in the urine. However, if glomerular disorders occur, albumin is one of the first proteins to “pass through” and is thus present in increased concentrations in the urine.
Albumin is one of the marker proteins in urine. These allow differentiation and follow-up of nephropathies (kidney diseases).One can distinguish microalbuminuria from macroalbuminemia.
The procedure
Material needed
- 2. morning urine
- 24 h urine (collected urine)
Preparation of the patient
- Not necessary
Disruptive factors
- Not known
Standard values
| Sample | Normal values |
| Temporary collected urine | < 20 μg/min |
| 24 h urine | <30 mg/die |
| Morning spontaneous urine | <20 mg/l<20 mg/g urine creatinine |
Values microalbuminuria
| Sample | Normal values |
| Temporary collected urine | 20-200 μg/min |
| 24 h urine | 30-300 mg/die |
| Morning spontaneous urine | 20-200 mg/l20-200 mg/g urine creatinine |
Values macroalbuminuria
| Sample | Normal values |
| Temporary collected urine | > 200 μg/min |
| 24 h urine | > 300 mg/die |
| Morning spontaneous urine | > 200 mg/l> 200 mg/g urine creatinine |
Indications
- Suspected glomerulonephritis – kidney disease, with inflammation of the kidney filterlets (glomeruli).
- Control examination in diabetes mellitus (diabetes).
Interpretation
Interpretation of increased values
- Diabetic nephropathy – kidney disease due to vascular disease in the presence of diabetes mellitus (diabetes).
- Glomerulonephritis
Interpretation of decreased values
- Not relevant to the disease
Note
- Patients with albuminuria have kidney disease even if the glomerular filtration rate (GFR) is ≥ 90!For the definition of chronic renal failure, see “Chronic renal failure/classification” below.
- Serum creatinine-based eGFR (estimated GFR; estimated glomerular filtration rate) and urine-based albumin-creatinine ratio (ACR) are appropriate parameters for cardiovascular risk assessment (at least with regard to mortality and heart failure/heart failure) according to one study. The ACR was a stronger risk factor than smoking, hypertension (high blood pressure), and hyperlipidemia (dyslipidemia) across all risk populations, while eGFR had about equal predictive value.
- Patients with albuminuria have a 35% increased risk of mild cognitive impairment or dementia (OR 1.35, 95%)
- Marker proteins in urine are:
- Albumin – molecular weight (MG) 66,000; marker for glomerular proteinuria (increased excretion of protein in the urine due to damage to the glomerula (renal corpuscles)).
- Transferrin – MG 90,000; marker for glomerular proteinuria.
- Immunoglobulin G (IgG) – MG 150,000; marker for unselective glomerular proteinuria (indicative of severe glomerular damage).
- Alpha-1 microglobulin – MG 33,000; marker for tubular proteinuria (restriction of tubular reabsorption function).
- Alpha-2-macroglobulin.- MG 750,000; marker for postrenal proteinuria caused by bleeding (e.g., stones, infections, injuries, tumors).