We can either measure the total urine protein or just the albumin fraction. Urine albumin measurements are better validated in regard to association with risk for chronic kidney disease progression and cardiovascular events.
*** Microalbuminuria and Macroalbuminuria have new terminologies which are moderately increased albuminuria and severely increased albuminuria.
Albuminuria
Albuminuria is graded as follows:
1. Normal to mildly increased albuminuria
-Albumin excretion rate: <30 mg/24 hours. i.e. The normal rate of albumin excretion is less than 30 mg/day (20 mcg/min);
-Albumin-to-creatinine ratio (ACR): <30 mg/g.
2. Moderately increased albuminuria (formerly called Microalbuminuria)
-Albumin excretion rate: 30-300 mg/24 hours.
-Albumin-to-creatinine ratio (ACR): 30-300 mg/g.
-Associated with increased risk of progressive kidney disease and cardiovascular events.
3. Severely increased albuminuria (formerly called Macroalbimunuria, overt proteinuria, etc)
-Albumin excretion rate: >300 mg/24 hours.
-Albumin-to-creatinine ratio (ACR): >300 mg/g.
-Larger amounts of proteinuria are associated with worse renal survival. These patients should be referred to a nephrologist.
-Severely increased albuminuria was formerly called macroalbuminuria, overt proteinuria, clinical renal disease, or dipstick positive proteinuria.
Note: You need to have at least 2 of 3 specimens fall within the moderately increased or severely increased albuminuria range over a 3 to 6 month period to classify a proteinuria into any of those two classes.
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Nephrotic-range proteinuria
-Urine total protein: ≥3.5 g/day.
-The presence of nephrotic-range proteinuria with edema, hypoalbuminemia (<3.0 g/dL), and hyperlipidemia is defined as nephrotic syndrome.
-Macroalbuminuria is a type of nephrotic range proteinuria.
Moderately and Severely Increased Albuminuria (formerly Microalbuminuria and Macroalbuminuria)
The normal rate of albumin excretion is less than 30 mg/day (20 mcg/min);
Moderately Increased Albuminuria (formerly Microalbuminuria) – Persistent albumin excretion between 30 and 300 mg/day (20 to 200 mcg/min) is called moderately increased albuminuria (formerly called “microalbuminuria“).
Severely increased albuminuria (formerly Macroalbuminuria) – Albumin excretion above 300 mg/day (200 mcg/min) is considered to represent severely increased albuminuria (formerly called “macroalbuminuria”, and which is also called overt proteinuria, clinical renal disease, or dipstick positive proteinuria)
Urine albumin-to-creatinine ratio (ACR)
An ACR of 30 to 300 mg/g suggests that albumin excretion is between 30 and 300 mg/day which is classified as moderately increased albuminuria.
ACR values above 300 mg/g (or 34 mg/mmol) define severely increased albuminuria (formerly called “macroalbuminuria”).
This classification system requires that at least 2 of 3 specimens fall within the moderately increased or severely increased albuminuria range over a three- to six-month period.
“The definition of microalbuminuria is albumin-creatinine ratio (ACR) of 30 to 300 mg/g, and of macroalbuminuria, ACR greater than 300 mg/g” NKF
** Don’t use a urine dipstick to assess protein excretion. It is very insensitive. It doesn’t become positive until protein excretion exceeds 300 t0 500 mg/day. Note that the upper limit of normal is 150 mg/day and most people excrete less than 100 mg/day.
What’s the difference between microalbuminuria and proteinuria?
Classification of Proteinuria.
Reference
http://us.bestpractice.bmj.com/best-practice/monograph/875.html
Kidney Int Suppl (2011). 2013 Jan;3(1):19-62. https://www.ncbi.nlm.nih.gov/pubmed?term=25018975
http://www2.kidney.org/professionals/kdoqi/guideline_diabetes/cpr1.htm