From the Guidelines
Microalbuminuria and proteinuria are distinct conditions, with microalbuminuria being an early indicator of kidney damage, and proteinuria indicating more significant kidney damage, as defined by the albumin-to-creatinine ratio (ACR) 1.
Key Differences
- Microalbuminuria refers to small amounts of albumin (30-300 mg/day) leaking into the urine, representing an early sign of kidney damage, particularly in conditions like diabetes and hypertension.
- Proteinuria is a broader term indicating larger amounts of protein in the urine (>300 mg/day), which suggests more significant kidney damage.
Diagnosis and Screening
- Regular screening for microalbuminuria is recommended for diabetic patients and those with hypertension, as early detection allows for interventions that can slow kidney disease progression 1.
- The terms “microalbuminuria” and “macroalbuminuria” are no longer used, instead, albuminuria is defined as UACR ≥30 mg/g, and persistent increased albuminuria in the range of UACR 30–299 mg/g is an early indicator of diabetic kidney disease in type 1 diabetes and a marker for development of diabetic kidney disease in type 2 diabetes 1.
Treatment and Management
- Treatment typically involves blood pressure control with ACE inhibitors or ARBs, blood glucose management in diabetics, and lifestyle modifications including reduced sodium intake, smoking cessation, and weight management.
- ACE inhibitors have been shown to reduce major CVD outcomes (i.e., MI, stroke, death) in patients with diabetes, thus further supporting the use of these agents in patients with elevated albuminuria, a CVD risk factor 1.
- ARBs do not prevent onset of elevated albuminuria in normotensive patients with type 1 or type 2 diabetes; however, ARBs have been shown to reduce the progression rate of albumin levels from 30 to 299 mg/24 h to levels ≥300 mg/24 h as well as ESRD in patients with type 2 diabetes 1.
Outcome
- Detecting microalbuminuria before it progresses to overt proteinuria is crucial for preserving kidney function, as it represents a window of opportunity when kidney damage may still be reversible 1.
- Patients with persistent albuminuria (30–299 mg/24 h) who progress to more significant levels (≥300 mg/24 h) are likely to progress to ESRD 1.
From the Research
Definition and Significance
- Microalbuminuria is defined as a persistent elevation of albumin in the urine of >30 to <300 mg/d (>20 to <200 microg/min) 2
- Proteinuria is a condition characterized by an excess of protein in the urine, often indicating kidney damage or disease 3
- Both microalbuminuria and proteinuria are early markers for potentially serious renal disease and are associated with increased risk of atherosclerotic cardiovascular disease 3
Diagnosis and Screening
- Screening of diabetics for microalbuminuria should occur in the primary care setting 3
- The morning spot urine test for albumin-to-creatinine measurement (mg/g) is recommended as the preferred screening strategy for all patients with diabetes and with the metabolic syndrome and hypertension 2
- Microalbuminuria should be assessed annually in all patients and every 6 months within the first year of treatment to monitor the impact of antihypertensive therapy 2
Treatment and Management
- Reduction of microalbuminuria in diabetics may retard its progression to overt diabetic nephropathy 3
- Therapy of renal diseases should aim for optimal blood pressure control and the maximum possible reduction in urinary protein excretion 3
- Angiotensin-converting enzyme inhibitor (ACE-I) and/or angiotensin-receptor blocker (ARB) therapy is the most effective measure to achieve this 3, 4
- ACE-I can reduce urinary albumin excretion significantly, despite similar antihypertensive efficacy to other medications such as amlodipine 5
Progression and Determinants
- Microalbuminuria can progress to proteinuria, and poor glycemic control and elevated serum cholesterol are major determinants/predictors of this progression 6
- Treatment with ACE-I may not be completely effective in preventing progression of microalbuminuria to proteinuria, and the mechanisms responsible for this are not clear 6