Albuminuria

• Indicator of kidney damage and / or a biomarker of systemic diseases dates back to 1969, when elevated albumin levels were first demonstrated in the urine of patients with newly diagnosed diabetes.

• Urine dipstick is a relatively insensitive marker for albuminuria, not becoming positive until albumin excretion exceeds 300-500 mg/day. 
• Normal rate of albumin excretion is < 30 mg/day (20 mcg/min).
• Persistent albumin excretion between 30-300 mg/day (20 to 200 mcg/min) is called moderately increased albuminuria (formerly called "microalbuminuria").
• Excretion > 300 mg/day (200 mcg/min) represents overt or dipstick positive proteinuria (severely increased albuminuria [formerly called "macroalbuminuria"].

• Albuminuria reflects functional and / or structural changes in the glomerular filtration membrane that allow increased leakage of albumin into primary urine in amounts exceeding the reabsorption capacity of the proximal nephron tubules. 
• Albuminuria considered as an indicator of early damage (dysfunction) of the vascular endothelium (including the glomerular vessels), which leads to increased permeability of the vascular wall. 

• Relationship between albuminuria and cardiovascular risk has been shown in studies of the general population. 
• It is linear and risk is independent of eGFR. 
• Associated with arterial stiffness assessed by the pulse wave velocity measurement