What is the interpretation of a urine albumin-to-creatinine (A/C) ratio with microalbumin <0.2 and creatinine at a level indicating normal renal function?

Interpretation of Urine Albumin-to-Creatinine Ratio with Microalbumin <0.2 and Creatinine 95

A urine albumin-to-creatinine ratio with microalbumin <0.2 mg/dL and creatinine 95 mg/dL indicates normal renal function with no evidence of microalbuminuria. This result falls well within normal limits and suggests healthy kidney function.

Understanding the Albumin-to-Creatinine Ratio (ACR)

The albumin-to-creatinine ratio is calculated as follows:

• ACR = (albumin in mg/dL) ÷ (creatinine in g/dL)
• Since creatinine is typically reported in mg/dL, we convert: 95 mg/dL = 0.95 g/dL
• Therefore, ACR = (<0.2 mg/dL) ÷ (0.95 g/dL) = <21 mg/g

According to the National Kidney Foundation guidelines, normal ACR values are defined as:

• Normal: ≤30 mg/g creatinine 1
• Microalbuminuria: >30 to 300 mg/g creatinine 1
• Macroalbuminuria: >300 mg/g creatinine 1

Clinical Significance

The calculated ACR of <21 mg/g is below the threshold of 30 mg/g, indicating:

• No evidence of microalbuminuria
• Normal kidney function
• No indication of early diabetic nephropathy or other kidney damage

Recommendations for Follow-up

Based on these normal findings:

• For patients without risk factors: Routine annual screening is appropriate 1
• For patients with diabetes: Continue annual screening for microalbuminuria 1
• For patients with hypertension or family history of CKD: Annual screening is recommended 1

Important Considerations

1. Proper Collection Technique:

   • First-morning urine samples are preferred to avoid orthostatic proteinuria 1
   • Patients should avoid vigorous exercise for 24 hours before sample collection 1

2. Potential False Negatives/Positives:

   • Transient elevations in urinary albumin can occur with:
     • Short-term hyperglycemia
     • Exercise
     • Urinary tract infections
     • Marked hypertension
     • Heart failure
     • Acute febrile illness 1

3. Confirmation of Results:

   • If microalbuminuria is suspected despite normal results, repeat testing is recommended
   • Persistent microalbuminuria is defined as 2 of 3 measurements above the reference range 1

Clinical Algorithm for ACR Interpretation

1. Normal ACR (<30 mg/g):

   • Continue routine annual screening
   • Optimize management of any underlying conditions (diabetes, hypertension)

2. Microalbuminuria (30-300 mg/g):

   • Confirm with repeat testing (2 of 3 samples over 3-6 months)
   • If confirmed, initiate ACE inhibitor or ARB therapy
   • Optimize blood pressure control (<130/80 mmHg)
   • Optimize glycemic control if diabetic (HbA1c <7%)
   • Retest within 6 months to assess treatment response 1

3. Macroalbuminuria (>300 mg/g):

   • Confirm with repeat testing
   • Aggressive treatment with ACE inhibitor/ARB
   • Consider nephrology referral

The current result of <21 mg/g places the patient firmly in the normal category, indicating healthy kidney function with no evidence of early kidney damage.