Creatinine variation propagated into eGFR and threshold marginLive current inputs
Health & Fitness
Kidney Function Target Range Calculator
Carry plausible creatinine variation through the 2021 CKD-EPI equation to show an eGFR planning band, category crossings, and the margin to a user-entered decision threshold without inventing a personal treatment target.
Central indexed eGFR—
Variation-derived eGFR band—
Band width—
Threshold crossing—
Central threshold margin—
De-indexed estimate band—
G categories spanned—
Decision message—
Uncertainty fan
Creatinine variation propagated into eGFR and threshold margin
The fan widens from the central laboratory value into lower and upper eGFR estimates, with the entered decision threshold drawn as a separate reference line.
Five-point sensitivity ledger
eGFR across the entered creatinine allowance
The table shows five equally spaced creatinine cases, their category context, and distance from the comparison threshold.
| Case | Creatinine | Indexed eGFR | G category | Vs threshold |
|---|
Band setup
Use a comparison threshold only when its source is explicit
- Enter the central standardized creatinine result.
- Choose a variation allowance for sensitivity analysis, not as a laboratory claim.
- Enter a threshold from the actual clinical or medication context.
- Check whether the whole band, not just the center, lies on one side.
- Confirm the appropriate equation and units before acting.
Why the band is asymmetric
The CKD-EPI power function amplifies equal percentage changes differently
A ten-percent creatinine rise does not subtract a fixed number of eGFR units, and a ten-percent fall does not add the same number back.
The output is a sensitivity range, not a confidence interval and not a personal target. It is designed to reveal fragile decisions close to a threshold.
Band propagation
Vary the measured input, not the final eGFR by an arbitrary percentage
Low and high creatinine cases are calculated first. Each case then passes through the nonlinear CKD-EPI equation. Because creatinine and eGFR move inversely and nonlinearly, the resulting eGFR band is asymmetric.
Detailed calculation process and general formulas
SCr_low = SCr x (1 - v)SCr_high = SCr x (1 + v)eGFR_j = CKD-EPI-2021(SCr_j, age, sex)margin_j = eGFR_j - TGFR_abs,j = eGFR_j x BSA / 1.73Symbols, meanings, and units
- v
- entered creatinine variation allowancedecimal
- j
- low, central, or high creatinine casecase
- T
- user-entered decision comparison thresholdmL/min/1.73 m2
- BSA
- Mosteller body surface aream2
- margin
- eGFR minus comparison thresholdmL/min/1.73 m2
Threshold robustness
Three possible relationships to the decision line
A band may sit entirely above, entirely below, or cross a threshold.
Above throughout
—All modeled cases exceed the entered line, though clinical context can still change the decision.
Crossing
—Reasonable input variation changes which side of the line the estimate occupies.
Below throughout
All modeled cases remain below the entered line; this still does not select treatment by itself.
Decision takeaway: A threshold crossing is a reason to verify measurement, equation, and context—not to average the values.
Applied decisions
Sensitivity questions the band can answer
Estimate near eGFR 60
The central estimate is close to a staging boundary.
What the result clarifies: The fan shows whether modest creatinine variation spans more than one G category.
Medication cutoff discussion
A label uses a kidney-function cutoff.
What the result clarifies: The calculator exposes margin but does not choose the dose or equation.
Worked default scenario
Current-input substitution and reconciliation
Method references
Evidence used to frame this specific model
Scope and limitations
This is a mathematical sensitivity analysis, not a clinical target, confidence interval, diagnosis, or medication instruction. Laboratory variation and non-GFR determinants of creatinine require professional interpretation.
Kidney Function Target Range Calculator | eGFR Uncertainty and Decision Band FAQ
Is the band a 95% confidence interval?
No. It is produced solely from the variation allowance you enter.
Which side of the band is worse?
Higher creatinine generally yields lower eGFR in this equation, but the clinical meaning depends on context and chronicity.
Can I set any threshold?
Mathematically yes, but it is meaningful only if it comes from a relevant guideline, drug label, or clinician.
Why not vary eGFR directly?
Propagating creatinine through the equation preserves the actual nonlinear relationship.