At what albumin-to-creatinine ratio (ACR) should I refer a patient to nephrology?

From the Guidelines

Refer patients to nephrology when their albumin-to-creatinine ratio (ACR) is persistently ≥300 mg/g or when there is a continuously rising UACR and/or continuously declining eGFR, as these are indicators of severe kidney damage and increased risk of cardiovascular morbidity and mortality. When considering referral, it's essential to confirm the elevated ACR with at least two measurements over 3-6 months, as transient elevations can occur due to various factors such as fever, exercise, or uncontrolled hypertension 1. While awaiting nephrology consultation, initiate ACE inhibitors or ARBs if the patient has hypertension, optimize blood pressure control (target <130/80 mmHg), improve glycemic control in diabetic patients, and address other cardiovascular risk factors 1. Key considerations for referral include:

• Uncertainty about the etiology of kidney disease
• Difficult management issues, such as anemia, secondary hyperparathyroidism, or significant increases in albuminuria despite good blood pressure management
• Advanced kidney disease (eGFR <30 mL/min/1.73 m²) requiring discussion of renal replacement therapy for ESRD 1 Early referral is crucial because albuminuria is a marker of kidney damage and cardiovascular risk, and specialist input can help slow the progression of kidney disease through targeted interventions and medication adjustments. The most recent and highest quality study, 1, published in 2024, emphasizes the importance of referral to a nephrologist for patients with continuously rising UACR levels and/or continuously declining eGFR, as well as those with advanced kidney disease or difficult management issues.

From the Research

Referral to Nephrology Based on Albumin-to-Creatinine Ratio (ACR)

• The decision to refer a patient to nephrology based on the albumin-to-creatinine ratio (ACR) is guided by clinical practice guidelines that consider both the estimated glomerular filtration rate (eGFR) and the level of albuminuria 2.
• According to the Kidney Disease: Improving Global Outcomes clinical practice guidelines, nephrology referral is recommended for patients with an eGFR < 30 ml/min/1.73m2 or a urinary albumin/creatinine ratio ≥ 300 mg/g 2.
• A study published in the Journal of Clinical Hypertension emphasizes the importance of albuminuria as a risk marker for adverse cardiovascular and renal outcomes, suggesting that routine annual screening for albuminuria can help identify patients at risk who may benefit from nephrology referral 3.
• The American Family Physician recommends nephrology consultation for patients with an estimated glomerular filtration rate less than 30 mL per minute per 1.73 m2, persistent urine albumin/creatinine ratio greater than 300 mg per g, or evidence of rapid loss of kidney function 4.
• Another study published in Nefrologia highlights the predictive value of combining eGFR and ACR for estimating the risk of progression to end-stage renal disease (ESRD) and cardiovascular mortality, which can inform decisions about nephrology referral 5.

Key Thresholds for Referral

• Urinary albumin/creatinine ratio ≥ 300 mg/g 2, 4
• eGFR < 30 ml/min/1.73m2 2, 4
• Evidence of rapid loss of kidney function 4

Importance of Albuminuria Testing

• Underutilization of albuminuria testing may be a barrier to identifying patients at elevated risk of kidney failure who may warrant nephrology referral 2.
• Routine annual screening for albuminuria is recommended for patients with risk factors such as diabetes, hypertension, and a history of cardiovascular disease 3, 4.