How often should we check Albumin-to-Creatinine Ratio (ACR) in patients with diabetes or hypertension?

Frequency of Albumin-to-Creatinine Ratio (ACR) Testing in Diabetes and Hypertension

For patients with diabetes or hypertension, ACR should be assessed at least annually, with more frequent monitoring (every 6 months) for those with established chronic kidney disease (CKD) or elevated ACR values. 1

Recommended Testing Frequency Based on Patient Population

Diabetes Patients

• Type 1 diabetes:

  • Begin screening after 5 years of disease duration 1
  • Test annually thereafter 1

• Type 2 diabetes:

  • Begin screening at diagnosis 1
  • Test annually thereafter 1

Hypertension Patients

• Test annually for all patients with hypertension 1

Increased Monitoring Frequency

More frequent monitoring (1-4 times per year) is recommended for:

• Patients with established CKD 1
• Patients with eGFR <60 mL/min/1.73 m² 1
• Patients with albuminuria (ACR ≥30 mg/g) 1

The specific monitoring frequency should follow this algorithm:

1. If normal ACR (<30 mg/g) and normal eGFR (≥60 mL/min/1.73 m²): Annual testing
2. If elevated ACR (≥30 mg/g) OR reduced eGFR (<60 mL/min/1.73 m²): Test every 6 months
3. If both elevated ACR and reduced eGFR: Test every 3-4 months based on CKD stage

Confirming Elevated ACR Results

Due to high day-to-day variability in albumin excretion (up to 40-50%), an elevated ACR should be confirmed with repeat testing:

• After an initial elevated ACR result, obtain 2 additional tests over the next 3-6 months 1
• Diagnosis of albuminuria requires at least 2 out of 3 positive tests 1

Clinical Considerations and Caveats

High Variability in ACR Measurements

Recent evidence shows significant within-individual variability in ACR measurements (coefficient of variation 48.8%), with repeat measurements potentially varying by a factor of 0.26 to 3.78 times the initial value 2. This variability highlights the importance of:

• Using morning spot urine samples when possible 1
• Confirming abnormal results with repeat testing
• Avoiding measurement during urinary tract infections or other conditions that may temporarily affect results 1

Risk Stratification

ACR is a powerful predictor of mortality and cardiovascular risk across all age groups and eGFR levels 3. Even mildly elevated ACR (9-14 mg/g) has been associated with incident hypertension 4, emphasizing the importance of regular monitoring.

Treatment Monitoring

For patients on ACE inhibitors or ARBs (standard treatment for diabetic kidney disease with albuminuria), regular ACR monitoring helps assess treatment effectiveness 1. The goal should be to achieve at least a 30-50% reduction in ACR, ideally to <30 mg/g 1.

Cost-Effectiveness

Annual ACR screening is cost-effective for both type 1 and type 2 diabetes patients, with type 2 diabetes showing even greater cost-effectiveness 5.

By following these evidence-based recommendations for ACR monitoring frequency, clinicians can optimize early detection of kidney disease, enable timely intervention, and improve long-term outcomes for patients with diabetes and hypertension.