How is Gfr Calculated

GFR (Glomerular Filtration Rate) Calculator (CKD-EPI 2021)

Female Male

function calculateGFR() { var serumCreatinine = parseFloat(document.getElementById('serumCreatinine').value); var age = parseInt(document.getElementById('age').value); var sex = document.getElementById('sex').value; if (isNaN(serumCreatinine) || serumCreatinine <= 0) { document.getElementById('gfrResult').innerHTML = 'Please enter a valid Serum Creatinine value (e.g., 0.9).'; return; } if (isNaN(age) || age 120) { document.getElementById('gfrResult').innerHTML = 'Please enter a valid Age between 18 and 120 years.'; return; } var kappa, alpha, sexFactor; if (sex === 'female') { kappa = 0.7; alpha = -0.241; sexFactor = 1.012; } else { // male kappa = 0.9; alpha = -0.302; sexFactor = 1; } var min_scr_kappa = Math.min(serumCreatinine / kappa, 1); var max_scr_kappa = Math.max(serumCreatinine / kappa, 1); var gfr = 142 * Math.pow(min_scr_kappa, alpha) * Math.pow(max_scr_kappa, -1.200) * Math.pow(0.9938, age) * sexFactor; document.getElementById('gfrResult').innerHTML = '

Estimated GFR: ' + gfr.toFixed(2) + ' mL/min/1.73m²

' + 'This GFR is estimated using the CKD-EPI 2021 equation.'; }

Understanding GFR (Glomerular Filtration Rate) and Its Calculation

What is GFR?

Glomerular Filtration Rate (GFR) is a crucial measure of kidney function. It represents the volume of blood filtered by the glomeruli (tiny filters in the kidneys) per unit of time. A healthy GFR indicates that your kidneys are effectively removing waste products and excess fluid from your blood. A reduced GFR can signal kidney damage or disease.

Why is GFR Important?

Monitoring GFR is vital for:

• Detecting Kidney Disease: Early detection of chronic kidney disease (CKD) allows for timely intervention and management.
• Staging CKD: GFR values are used to classify the stage of kidney disease, guiding treatment decisions.
• Medication Dosing: Many medications are cleared by the kidneys, and their dosages may need adjustment based on GFR to prevent toxicity.
• Assessing Treatment Effectiveness: Changes in GFR can indicate whether treatments for kidney conditions are working.

How is GFR Measured?

Direct measurement of GFR is complex and typically involves injecting a marker substance (like inulin or iohexol) and measuring its clearance from the blood. For routine clinical practice, GFR is usually estimated (eGFR) using formulas that incorporate readily available blood test results.

The CKD-EPI 2021 Equation

Our calculator uses the CKD-EPI (Chronic Kidney Disease Epidemiology Collaboration) 2021 equation. This is one of the most widely accepted and accurate formulas for estimating GFR. A significant advancement of the 2021 equation is that it is race-neutral, meaning it does not include a race variable, addressing concerns about health disparities and improving equity in kidney disease diagnosis.

The formula takes into account:

• Serum Creatinine (Scr): A waste product from muscle metabolism that is filtered by the kidneys. Higher levels can indicate reduced kidney function.
• Age: Kidney function naturally declines with age.
• Sex: Biological sex influences muscle mass and creatinine production.

Interpreting Your GFR Results

GFR is typically reported in milliliters per minute per 1.73 square meters (mL/min/1.73m²), which adjusts for average body surface area. Here's a general guide to GFR stages:

• GFR 90 or higher: Normal kidney function.
• GFR 60-89: Mildly decreased kidney function. Often no symptoms, but may indicate early kidney disease.
• GFR 45-59: Mild to moderate decrease in kidney function.
• GFR 30-44: Moderate to severe decrease in kidney function.
• GFR 15-29: Severely decreased kidney function.
• GFR less than 15: Kidney failure, often requiring dialysis or kidney transplant.

It's important to note that a single GFR reading should always be interpreted in the context of your overall health, medical history, and other lab results. Factors like diet, hydration, and certain medications can temporarily affect creatinine levels.

Example Calculation:

Let's consider a 45-year-old female with a serum creatinine of 0.9 mg/dL:

• Serum Creatinine: 0.9 mg/dL
• Age: 45 years
• Sex: Female

Using the CKD-EPI 2021 formula, the estimated GFR would be approximately 98.5 mL/min/1.73m², which falls within the normal range.

Disclaimer:

This calculator provides an estimated GFR based on the CKD-EPI 2021 equation and should be used for informational purposes only. It is not a substitute for professional medical advice, diagnosis, or treatment. Always consult with a qualified healthcare professional for any health concerns or before making any decisions related to your health or treatment.