Elevated Albumin-to-Creatinine Ratio: Diagnosis and Management
An elevated albumin-to-creatinine ratio (ACR) indicates kidney damage, most commonly due to diabetic kidney disease or hypertensive nephropathy, and requires treatment with ACE inhibitors or ARBs along with optimization of blood pressure and glycemic control to reduce progression to end-stage kidney disease and cardiovascular complications.
Definition and Classification
Albuminuria is categorized according to the KDIGO classification system:
| Albuminuria Category | ACR (mg/g creatinine) | Description |
|---|---|---|
| A1 | <30 | Normal to mildly increased |
| A2 | 30-299 | Moderately increased (formerly microalbuminuria) |
| A3 | ≥300 | Severely increased (formerly macroalbuminuria) |
Clinical Significance
Elevated ACR (≥30 mg/g) is a marker of kidney damage and an independent predictor of:
Even high-normal ACR values (10-30 mg/g) have been associated with increased risk of CKD progression in patients with type 2 diabetes 4 and cardiovascular mortality in patients with coronary artery disease 2
Diagnostic Considerations
Confirm elevated ACR with 2-3 specimens collected within a 3-6 month period due to high day-to-day variability (up to 48.8% coefficient of variation) 5, 3
Rule out transient causes of elevated ACR:
- Exercise within 24 hours
- Urinary tract infection
- Fever
- Congestive heart failure
- Marked hyperglycemia
- Menstruation
- Marked hypertension 3
Consider kidney biopsy if there are atypical features:
- Rapidly increasing albuminuria
- Active urinary sediment (red or white blood cells, cellular casts)
- Nephrotic syndrome
- Rapidly decreasing eGFR
- Absence of retinopathy (in type 1 diabetes) 3
Management Approach
1. Blood Pressure Control
- Target blood pressure <130/80 mmHg for patients with albuminuria 1
- First-line therapy:
2. Glycemic Control
- Optimize glycemic control, especially in patients with diabetes
- Annual screening for albuminuria and eGFR in patients with diabetes 3
- Begin screening 5 years after diagnosis of type 1 diabetes and at diagnosis of type 2 diabetes 3
3. Lifestyle Modifications
- Dietary protein intake should be approximately 0.8 g/kg body weight per day for patients with CKD stages 3-5 3, 1
- Higher protein intake may be appropriate for patients on dialysis 3
4. Monitoring
- Monitor ACR every 6 months if albuminuria persists 1
- Monitor eGFR at least annually, more frequently if <60 mL/min/1.73 m² 1
- Monitor serum creatinine and potassium when using ACE inhibitors, ARBs, or diuretics 3
- Do not discontinue ACE inhibitors or ARBs for minor increases in serum creatinine (≤30%) in the absence of volume depletion 3
5. Treatment Goals
- Aim for at least a 30% reduction in albuminuria 1
- Evaluate response to therapy by monitoring changes in ACR and eGFR 1
When to Refer to Nephrology
Refer patients to a nephrologist if:
- eGFR <30 mL/min/1.73 m² 3
- Persistent significant albuminuria (≥300 mg/g) 1
- Unclear etiology of kidney disease 3
- Rapidly increasing albuminuria or rapidly declining eGFR 1
- Active urinary sediment 3
- Difficult management issues 3
Common Pitfalls to Avoid
- Relying on a single ACR measurement due to high biological variability 5
- Failing to consider transient causes of elevated ACR 1
- Discontinuing ACE inhibitors or ARBs for minor increases in serum creatinine 3
- Delaying treatment in patients with confirmed albuminuria 1
- Overlooking the need for gender-specific interpretation (women have lower creatinine excretion, affecting ACR interpretation) 6
By following this structured approach to diagnosis and management, patients with elevated ACR can receive appropriate care to slow CKD progression and reduce cardiovascular risk.