GFR Calculator Cockcroft-Gault Formula

Cockcroft-Gault Formula:

\[ CrCl = \frac{(140 - Age) \times Weight \times (0.85 \text{ if female})}{72 \times Scr} \]

Age:

years

Weight:

Serum Creatinine (Scr):

mg/dL

Gender:

Creatinine Clearance (CrCl):

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1. What is the Cockcroft-Gault Formula?

The Cockcroft-Gault formula estimates creatinine clearance (CrCl) from serum creatinine, age, weight, and gender. It is widely used for drug dosing adjustments in patients with renal impairment and provides an estimate of glomerular filtration rate (GFR).

2. How Does the Calculator Work?

The calculator uses the Cockcroft-Gault formula:

\[ CrCl = \frac{(140 - Age) \times Weight \times (0.85 \text{ if female})}{72 \times Scr} \]

Where:

\( Age \) — Age in years
\( Weight \) — Body weight in kilograms
\( Scr \) — Serum creatinine in mg/dL
\( 0.85 \) — Adjustment factor for female gender

Explanation: The formula estimates creatinine clearance based on the premise that creatinine production decreases with age and differs between genders, while accounting for body size through weight.

3. Importance of CrCl Calculation

Details: Creatinine clearance estimation is essential for appropriate drug dosing in patients with renal impairment, assessing kidney function, and monitoring renal toxicity of medications.

4. Using the Calculator

Tips: Enter age in years, weight in kilograms, serum creatinine in mg/dL, and select gender. All values must be valid (age 1-120 years, weight > 0 kg, creatinine > 0 mg/dL).

5. Frequently Asked Questions (FAQ)

Q1: Why use Cockcroft-Gault instead of other GFR equations?
A: Cockcroft-Gault is specifically validated for drug dosing adjustments and is widely referenced in pharmaceutical literature and clinical guidelines.

Q2: What are normal CrCl values?
A: Normal CrCl is approximately 90-120 mL/min for young adults, decreasing with age. Values below 60 mL/min indicate renal impairment.

Q3: When should ideal body weight be used?
A: For obese patients (BMI > 30), some guidelines recommend using ideal body weight rather than actual weight to avoid overestimating CrCl.

Q4: Are there limitations to this formula?
A: Less accurate in elderly patients, those with extreme body weights, muscle wasting conditions, or rapidly changing renal function.

Q5: Can this be used for all drug dosing?
A: While widely used, some drugs require more precise GFR estimation methods. Always consult specific drug prescribing information.