Diabetic Nephropathy Classification and Management

Classification System

The American Diabetes Association recommends a comprehensive classification system for diabetic nephropathy based on glomerular filtration rate (GFR) and albuminuria levels, which predicts the risk of progression to end-stage renal disease 1
The classification system includes five GFR stages (G1-G5) and three albuminuria categories (A1-A3), with GFR stages defined as: G1 (≥90 mL/min/1.73 m²), G2 (60-89 mL/min/1.73 m²), G3a (45-59 mL/min/1.73 m²), G3b (30-44 mL/min/1.73 m²), G4 (15-29 mL/min/1.73 m²), and G5 (<15 mL/min/1.73 m²) 1
Albuminuria categories are defined as: A1 (<30 mg/g creatinine), A2 (30-299 mg/g creatinine), and A3 (≥300 mg/g creatinine) 1, 2

The combination of GFR and albuminuria categories creates a matrix that predicts the risk of progression to end-stage renal disease, with stages A1/G1 and A1/G2 considered stable disease with low risk 2
The risk of progression increases as GFR decreases and albuminuria increases, with a color-coded system (green, yellow, orange, red, dark red) indicating increasing risk 1
Patients with stages A1/G1 and A1/G2 should undergo annual measurements, while those with higher risk categories require more frequent monitoring (at least once per year for yellow, twice per year for orange, three times per year for red, and four times per year for dark red) 1, 2

The albumin-to-creatinine ratio (ACR) from a spot urine sample is preferred over 24-hour collections for screening and diagnosis, with at least 2-3 measurements over a 6-month period recommended to confirm the diagnosis 1, 2
Exercise, infection, fever, heart failure, marked hyperglycemia, hypertension, pyuria, and hematuria can falsely elevate urinary albumin excretion 4

Patients with GFR <30 mL/min/1.73 m² or severely increased albuminuria (A3) should be referred to a nephrologist, regardless of GFR 1
Patients with atypical presentations (e.g., kidney disease without retinopathy in type 1 diabetes) should be considered for nephrology referral and possible kidney biopsy 1