How to calculate the estimated Glomerular Filtration Rate (eGFR) for a 53-year-old male patient with a serum creatinine level of 111 umol/L?

How to Calculate eGFR Step-by-Step for a 53-Year-Old Male with Creatinine 111 µmol/L

Use the CKD-EPI 2009 creatinine equation, which is the recommended formula by KDIGO guidelines for estimating GFR in adults, as it demonstrates superior accuracy compared to older equations like MDRD and Cockcroft-Gault. 1

Step 1: Convert Creatinine to mg/dL

• Serum creatinine = 111 µmol/L
• Conversion factor: divide by 88.4 1
• 111 ÷ 88.4 = 1.26 mg/dL

Step 2: Apply the CKD-EPI 2009 Equation

The CKD-EPI equation for males with creatinine >0.9 mg/dL is: 1, 2

eGFR = 141 × min(SCr/0.9,1)^-0.411 × max(SCr/0.9,1)^-1.209 × 0.993^age

Breaking Down the Calculation:

1. SCr/0.9 = 1.26/0.9 = 1.40

2. min(1.40,1) = 1.0 (use the smaller value)

3. max(1.40,1) = 1.40 (use the larger value)

4. Calculate each component:

   • 1.0^-0.411 = 1.0
   • 1.40^-1.209 = 0.629
   • 0.993^53 = 0.733

5. Final calculation:

   • eGFR = 141 × 1.0 × 0.629 × 0.733
   • eGFR = 65 mL/min/1.73 m²

Step 3: Interpret the Result

• This eGFR of 65 mL/min/1.73 m² falls in the 60-89 range, indicating Stage 2 CKD if kidney damage markers are present, or normal age-appropriate function if no damage markers exist. 2

• The result should be rounded to the nearest whole number as recommended by KDIGO. 1

Critical Next Steps

Measure urinary albumin-to-creatinine ratio (UACR) on a spot urine sample to determine if kidney damage is present (normal <30 mg/g), as this is the critical determinant of whether this eGFR represents CKD requiring intervention. 2

• If UACR is elevated, this patient has Stage 2 CKD and requires blood pressure optimization and monitoring 2-3 times yearly. 2

• If UACR is normal, annual monitoring of creatinine and eGFR is sufficient. 2

• Repeat creatinine measurement in 3-6 months to confirm stability, as single measurements can be affected by recent exercise, infection, or dietary protein intake. 2

Important Clinical Caveats

• At eGFR 65 mL/min/1.73 m², no routine medication dose adjustments are required for most renally-excreted drugs. 2

• The CKD-EPI equation is more accurate than MDRD at GFR ≥60 mL/min/1.73 m², which is why it is the preferred method. 1, 3, 4

• Do not rely on serum creatinine concentration alone to assess kidney function, as it can grossly overestimate GFR, particularly in older adults with reduced muscle mass. 1

• The CKD-EPI equation may be less accurate in extremes of body size, severe malnutrition, rapidly changing kidney function, or when calculating doses of potentially toxic renally-excreted drugs—in these situations, consider direct GFR measurement. 1, 5