CKD Stage Classification for GFR 37
A GFR of 37 mL/min/1.73 m² classifies as Stage 3b Chronic Kidney Disease, representing moderate-to-severe kidney function impairment that requires active monitoring and management of complications. 1
Stage 3b CKD Definition
Stage 3b CKD is defined by a GFR range of 30-44 mL/min/1.73 m², which encompasses your patient's GFR of 37 mL/min/1.73 m². 1, 2, 3
The subdivision of Stage 3 into 3a (GFR 45-59) and 3b (GFR 30-44) is clinically critical because these subgroups demonstrate significantly different mortality risks, cardiovascular event rates, and progression rates to kidney failure. 1, 2, 4
Stage 3b patients have approximately 3-fold higher risk of progression to advanced CKD compared to Stage 3a patients (HR 2.99,95% CI 2.19-4.10). 4
Complete CKD Classification Requirements
You must classify this patient using the complete CGA system (Cause, GFR category, Albuminuria category), not GFR alone. 1, 2
Measure albumin-to-creatinine ratio (ACR) on a spot urine sample to assign albuminuria category:
Albuminuria independently predicts cardiovascular mortality and progression to kidney failure, with macroalbuminuria conferring 3-fold increased risk of progression (HR 3.06). 4
Confirm that kidney abnormalities have persisted for at least 3 months to distinguish chronic from acute kidney disease. 1, 3
Clinical Action Plan for Stage 3b
At Stage 3b, your priorities are evaluating and treating complications, estimating progression rate, and preparing for potential nephrology referral. 1, 3
Immediate Management Steps:
Monitor serum creatinine and eGFR every 2-4 times per year based on stability and albuminuria level. 2
Screen for and manage CKD complications that become highly prevalent below GFR 45:
Optimize blood pressure control targeting ≤130/80 mmHg if albuminuria ≥30 mg/g, using ACE inhibitors or ARBs as first-line agents. 5
Review all medications for nephrotoxic agents (NSAIDs, aminoglycosides, contrast agents) and drugs requiring dose adjustment at this GFR level. 1, 6
Nephrology Referral Indications:
Refer to nephrology if any of the following are present: 3, 5
- GFR declines to <30 mL/min/1.73 m² (progression to Stage 4) 5
- Rapid decline in kidney function (>5 mL/min/1.73 m² per year or >25% decrease in eGFR) 5
- Albuminuria in A3 category (>300 mg/g) 2
- Refractory complications despite appropriate management 5
Prognosis and Risk Stratification
Stage 3b carries significantly elevated mortality risk compared to earlier stages, with hazard ratios of 2.75 for all-cause mortality and 11.0 for progression to kidney failure compared to Stages 1-2. 7
Approximately 48% of Stage 3 CKD patients do not progress over 10 years, while 17.3% progress to Stage 4 and 34.6% progress to Stage 5, with 26.2% ultimately requiring dialysis. 4
Independent predictors of progression include degree of albuminuria (most important), microscopic hematuria, and Stage 3b classification itself. 4
Common Pitfalls to Avoid
Do not rely on serum creatinine alone for staging—always calculate eGFR using validated equations (CKD-EPI preferred over MDRD). 1, 6
Do not classify based on GFR alone—incomplete staging without albuminuria assessment leads to inadequate risk stratification. 1, 2
Do not assume age-related GFR decline is "normal aging"—decreased GFR remains an independent predictor of adverse outcomes regardless of age and requires the same classification and management approach. 1, 3
Variability in eGFR measurements is itself an independent mortality risk factor (HR 1.40 for highest vs. lowest quartile of variability), so trending GFR over time provides additional prognostic information beyond single measurements. 8