When should the albumin (ACR) to creatinine ratio be checked in patients with risk factors for kidney disease, such as diabetes, hypertension, or cardiovascular disease?

When to Check Albumin-Creatinine Ratio (ACR)

All patients with diabetes, hypertension, or cardiovascular disease should be screened for albuminuria using spot urine ACR at least annually, with testing initiated 5 years after diagnosis for type 1 diabetes and immediately at diagnosis for type 2 diabetes. 1

Initial Screening Recommendations by Population

High-Risk Populations Requiring Annual Screening

• Diabetes mellitus patients: Begin ACR screening 5 years after diagnosis for type 1 diabetes (testing can be delayed until after puberty), but start immediately at diagnosis for type 2 diabetes due to uncertain disease onset 1

• Hypertension patients: Screen annually, as over 20% have undiagnosed albuminuria (ACR ≥30 mg/g), yet only 7% are currently tested 1

• Cardiovascular disease patients: Screen annually, as this population has CKD prevalence exceeding 40% 1

• Family history of CKD or ESRD: Annual screening recommended as part of regular health examination 1

Additional High-Risk Groups Warranting Individualized Screening

The following populations should undergo ACR testing based on clinical assessment and shared decision-making, rather than uniform annual screening 1:

• Older age (though chronologic age alone should not determine screening initiation) 1
• Systemic lupus erythematosus or HIV infection 1
• Prior acute kidney injury 1
• History of preeclampsia 1
• Obesity 1
• Exposure to nephrotoxic medications 1
• High-risk occupational or environmental exposures 1

Monitoring Frequency After Initial Diagnosis

For Patients with Normal or Mildly Increased Albuminuria (ACR <30 mg/g)

• Continue annual screening in all high-risk populations 1

For Patients with Moderately Increased Albuminuria (ACR 30-299 mg/g)

• eGFR ≥60 mL/min/1.73 m²: Monitor ACR and eGFR annually 1
• eGFR 45-59 mL/min/1.73 m²: Monitor every 6 months 1
• eGFR 30-44 mL/min/1.73 m²: Monitor every 3-4 months 1

For Patients with Severely Increased Albuminuria (ACR ≥300 mg/g)

• eGFR >60 mL/min/1.73 m²: Monitor ACR and eGFR every 6 months 1
• eGFR 30-60 mL/min/1.73 m²: Monitor every 3 months 1
• eGFR <30 mL/min/1.73 m²: Immediate nephrology referral required 1

Reassessment After Treatment Initiation

• Retest within 6 months after initiating antihypertensive therapy (particularly ACE inhibitors or ARBs) or lipid-lowering treatment to assess treatment response 1

• If treatment achieves significant reduction in albuminuria, return to annual monitoring 1

• If no reduction occurs despite treatment, evaluate whether blood pressure and lipid targets are met and whether renin-angiotensin-aldosterone system inhibitors are included in the regimen 1

Confirmation of Abnormal Results

Critical caveat: Due to high day-to-day variability in albumin excretion, confirm any ACR >30 mg/g with 2 out of 3 positive tests collected over 3-6 months before diagnosing persistent albuminuria 1

Factors That Can Falsely Elevate ACR

Exclude these transient causes before confirming chronic kidney disease 1:

• Vigorous exercise within 24 hours (patients should refrain from exercise for 24 hours before collection) 1
• Active urinary tract infection or fever 1
• Menstruation 1
• Marked hyperglycemia 1
• Uncontrolled hypertension 1
• Congestive heart failure exacerbation 1

Optimal Collection Method

• First morning void specimen is preferred for children, adolescents, and adults to minimize variability and avoid orthostatic proteinuria 1

• Spot untimed urine samples are acceptable and preferred over 24-hour collections, which are burdensome and add little accuracy 1

• Patients should avoid food intake for at least 2 hours before collection when possible 2

• Refrigerate samples for same-day or next-day assay; one freeze is acceptable if necessary, but avoid repeated freeze-thaw cycles 1

Why ACR Rather Than Albumin Alone

The creatinine measurement normalizes for urine concentration, eliminating false-positive and false-negative results that occur when measuring albumin concentration alone 1, 2. This makes spot urine ACR as accurate as timed collections without the inconvenience 2. The albumin-to-creatinine ratio also demonstrates the strongest correlation with renal events and cardiovascular outcomes in longitudinal studies 3.