The estimated glomerular filtration rate (eGFR) serves as an essential tool for assessing kidney function in clinical practice. It is calculated using serum creatinine levels and factoring in the patient’s age, gender, and race. This article will guide you step by step on how to calculate eGFR from creatinine.

Step 1: Measure Serum Creatinine

The starting point for calculating eGFR is obtaining a patient’s serum creatinine level. Creatinine is a waste product generated from normal muscle use and breakdown, with excess levels being filtered out by the kidneys. A blood test will provide an accurate measure of the creatinine level in your body.

Step 2: Choose an eGFR Formula

There are several formulas available for calculating eGFR, but the Modification of Diet in Renal Disease (MDRD) Study Equation and the Chronic Kidney Disease Epidemiology Collaboration (CKD-EPI) Equation are most commonly used. Both formulas consider age, gender, and race; however, the CKD-EPI equation is often considered more accurate, particularly for patients with mildly reduced kidney function.

MDRD Study Equation:

eGFR = 175 x (Serum Creatinine)^(-1.154) x (Age)^(-0.203) x (0.742 if female) x (1.210 if African American)

CKD-EPI Equation:

This equation requires a slightly more complex calculation based on serum creatinine levels; you can find the full CKD-EPI calculation here: https://www.kidney.org/content/mdrd-calculator

Or use online tools or apps designed specifically to compute eGFR values.

Step 3: Insert Patient Information

Now that you have chosen an appropriate equation, it’s time to input the patient’s details:

– Age: Input the patient’s age in years

– Gender: If the patient is female, multiply by the gender variable (0.742 for MDRD or make adjustments based on the CKD-EPI equation)

– Race: If the patient is African American, multiply by the race variable (1.210 for MDRD or follow specific accommodations in the CKD-EPI method)

– Serum Creatinine: Insert serum creatinine level (in mg/dL) at the appropriate place in your selected equation

Step 4: Perform the Calculation

With all variables in place, complete the required calculations to determine the eGFR value.

Step 5: Interpret eGFR Results

The eGFR result indicates patients’ kidney function and helps categorize chronic kidney disease (CKD) stages:

– Normal kidney function: eGFR ≥90 mL/min/1.73 m2

– Mild impairment: eGFR 60-89 mL/min/1.73 m2

– Stage 3 CKD: eGFR 30-59 mL/min/1.73 m2

– Stage 4 CKD: eGFR 15-29 mL/min/1.73 m2

– Stage 5 CKD (kidney failure): eGFR <15 mL/min/1.73 m2

Conclusion:

Calculating eGFR from creatinine is crucial for assessing kidney function, diagnosing CKD, and guiding treatment decisions. Understanding how to interpret eGFR results can facilitate timely interventions and promote optimal patient outcomes.