How is an abnormal eGFR (estimated Glomerular Filtration Rate) score managed?

Management of Abnormal eGFR

For patients with abnormal estimated Glomerular Filtration Rate (eGFR), management should begin with confirming the accuracy of the eGFR measurement using creatinine and cystatin C-based estimation (eGFRcr-cys), followed by implementing targeted interventions based on CKD stage and albuminuria level. 1

Confirming Abnormal eGFR

1. Initial Assessment:

   • Use serum creatinine (SCr) and an estimating equation for initial assessment of GFR 1
   • If eGFRcr is suspected to be inaccurate or if clinical decisions depend on precise GFR measurement, measure cystatin C and calculate eGFRcr-cys 1

2. Situations requiring more accurate GFR assessment:

   • Low muscle mass or altered creatinine generation
   • Use of medications affecting creatinine secretion
   • High-stakes clinical decisions (e.g., drug dosing, CKD staging)
   • Discrepancy between clinical presentation and eGFRcr 1

3. Verification process:

   • Repeat testing within 3-6 months to confirm chronicity 1
   • Two abnormal values at least 90 days apart confirm CKD diagnosis 1
   • Single measurements may overestimate CKD prevalence by approximately 25% 2

Management Based on CKD Stage

Stage G1-G2 (eGFR ≥60 mL/min/1.73m²) with Albuminuria

1. Monitor regularly:

   • Annual monitoring of eGFR and albuminuria 1
   • More frequent monitoring if rapid progression or comorbidities

2. Blood pressure control:

   • Target BP <130/80 mmHg
   • ACE inhibitor or ARB for those with albuminuria 30-299 mg/g creatinine 1
   • Monitor serum creatinine and potassium when using these medications 1, 3

Stage G3a (eGFR 45-59 mL/min/1.73m²)

1. All measures from earlier stages plus:

   • Consider nephrology referral if rapid progression or uncertain etiology
   • Avoid nephrotoxic medications
   • Adjust medication dosages as needed

2. Cardiovascular risk reduction:

   • Consider SGLT2 inhibitors for patients with diabetes and eGFR >30 mL/min/1.73m² 1
   • Consider GLP-1 receptor agonists for additional renal and cardiovascular protection 1

Stage G3b-G4 (eGFR 15-44 mL/min/1.73m²)

1. Enhanced monitoring:

   • Monitor eGFR and electrolytes every 3-6 months
   • Strongly recommended ACE inhibitor or ARB for those with albuminuria ≥300 mg/g creatinine 1
   • Avoid dual RAS blockade (e.g., combining ACE inhibitor and ARB) due to increased risk of hyperkalemia and acute kidney injury 3, 4

2. Additional interventions:

   • Dietary protein intake approximately 0.8 g/kg body weight per day 1
   • Nephrology referral for eGFR <30 mL/min/1.73m² 1

Stage G5 (eGFR <15 mL/min/1.73m²)

1. Preparation for kidney replacement therapy:
   • Urgent nephrology referral
   • Education about treatment options (dialysis, transplantation)
   • Vascular access planning if hemodialysis anticipated

Special Considerations

Medication Management

1. Drug dosing considerations:

   • eGFR should not be used directly for drug dosing without validation 5
   • For drugs cleared by kidneys, consider measured GFR or validated methods 1, 5
   • Monitor for drug toxicity with reduced kidney function

2. Medication precautions:

   • Avoid NSAIDs in patients with reduced eGFR 3
   • Monitor potassium levels when using ACE inhibitors or ARBs 3, 4
   • Adjust dosages of renally cleared medications

Monitoring Disease Progression

1. Assess rate of eGFR decline:

   • Normal age-related decline: ~1 mL/min/1.73m² per year
   • Rapid progression: >5 mL/min/1.73m² per year or >10% per year
   • Assess potential for error in eGFR when evaluating changes over time 1

2. Indications for nephrology referral:

   • eGFR <30 mL/min/1.73m² 1
   • Rapid progression (>5 mL/min/1.73m² per year)
   • Uncertainty about etiology
   • Difficult management issues 1

Common Pitfalls to Avoid

1. Relying solely on serum creatinine:

   • Serum creatinine alone is insufficient to assess kidney function 1
   • Use validated GFR estimating equations rather than serum creatinine alone 1

2. Using single eGFR measurements for diagnosis:

   • Single measurements overestimate CKD prevalence by ~25% 2
   • Confirm abnormal values with repeat testing

3. Ignoring non-GFR determinants:

   • Diet (vegetarian, high-protein, keto) affects creatinine levels 1
   • Muscle mass variations impact creatinine-based eGFR 1
   • Medications can alter creatinine secretion 1

4. Overlooking discrepancies between eGFRcr and eGFRcys:

   • Large differences between eGFRcr and eGFRcys may indicate increased cardiovascular risk 6
   • Understanding these differences can provide clinical insights 1

By following this structured approach to managing abnormal eGFR, clinicians can accurately assess kidney function, implement appropriate interventions, and optimize outcomes for patients with chronic kidney disease.