There are three albumin categories in urine measurement: A1, and A3. Albuminuria testing on a random or spot specimen is quantified in mg of urine albumin to gram of urine creatinine (mg/g) and is categorized as A1 or normal to mildly increased (less than 30 mg/g), A2 or moderately increased (30-300 mg/g), and A3 or severely increased (greater than 300 mg/g). Albuminuria categories were added to the classification of chronic kidney disease (CKD), since higher levels of albuminuria have been shown to be independently associated with mortality, cardiovascular disease and rate of progression to kidney failure.
Microalbuminuria is moderately increased urine level of ratio (ACR) 30-300 mg/g and described as A2 in the albumin category.
Macroalbuminuria is a severely increased urine level ACR greater than 300 mg/g and described as A3 in the albumin category.
Kidney Disease: Improving Global Outcomes (KDIGO) CKD Work Group. KDIGO 2012 clinical practice guideline for the evaluation and management of chronic kidney disease. Kidney Int Suppl. 2013;3:1-150.