The 2009 CKD-EPI Creatinine calculator is a tool used to estimate the glomerular filtration rate (GFR), which helps assess kidney function and determine the stage of chronic kidney disease (CKD). It takes into account several personal health factors to deliver a meaningful result.

Inputs include:
- Age, which should be a numerical value between 18 and 120 years.
- Gender, for which the options are "male" or "female."
- Serum Creatinine, given in either mg/dL (0.1 to 20) or μmol/L (1 to 1000). If provided in μmol/L, the tool converts this to mg/dL using a factor of 0.0113.
- Race, which can be "black" or "non-black" to account for race-related physiological differences.

In determining the estimated GFR, the calculator performs the following steps:
- Identifies parameters based on gender. Females use a kappa of 0.7 and an alpha of -0.329, while males use a kappa of 0.9 and an alpha of -0.411.
- It calculates the estimated GFR using a formula that incorporates these parameters, the age of the individual, and adjustments for gender and race.
- The calculation follows a specific formula: 141 multiplied by the function of serum creatinine levels over kappa, raised to the power of alpha, adjusting for the individual's age, gender, and race.

The results are:
- Estimated GFR in mL/min/1.73 m², rounding to the nearest whole number. This estimate reflects kidney filtration efficiency, with possible values ranging from 0 to 150.
- CKD Stage, which provides a clear understanding of kidney health:
  - Stage 1, indicating normal or high kidney function with a GFR of 90 or more.
  - Stage 2, mild reduction in function with GFR between 60 and 89.
  - Stage 3, moderate reduction with GFR between 30 and 59.
  - Stage 4, severe reduction with GFR between 15 and 29.
  - Stage 5, suggesting kidney failure with GFR below 15.

This method allows clinicians and patients to assess kidney health systematically, using key health metrics to guide potential management and treatment decisions.

The CKD-EPI equation estimates Glomerular Filtration Rate (GFR) using serum creatinine, age, sex, and race. It's more accurate than the MDRD equation, especially at higher GFR values, and is the current standard for estimating kidney function in clinical practice.

CKD-EPI Creatinine (2009)