Raw eGFR observations, fitted slope, and G-category backgroundLive current inputs
Health & Fitness
Kidney Function Trend Calculator
Analyze six dated eGFR observations with a least-squares annual slope, residual variability, category crossings, and recent-versus-older comparison while preserving every raw value.
Least-squares annual slope—
First-to-last change—
Six-result mean—
Residual variability—
Recent three-result mean—
Category movement—
Albuminuria context—
Trend signal—
Longitudinal kidney-function view
Raw eGFR observations, fitted slope, and G-category background
The chart keeps individual laboratory results visible over the fitted line, while shaded categories show when interpretation changes across boundaries.
Observation ledger
Six results with fitted value and residual
Each row shows the actual value, regression expectation, difference, category, and whether the point sits above or below the fitted path.
| Time | Observed eGFR | Fitted eGFR | Residual | G category |
|---|
Trend setup
Use comparable results and preserve their dates
- Use eGFR values produced by the same or clearly documented equations where possible.
- Enter the exact span from first to last result.
- Do not remove an inconvenient result without a documented reason.
- Add current urine ACR for complementary damage context.
- Discuss rapid or unexplained change with the treating team.
Slope and noise
A direction is easier to trust when scatter is small
Endpoint change can be distorted by an unusual first or last result. Regression uses all six points and reports the residual scatter that remains.
The slope still does not identify cause. Hydration, acute illness, medicines, assay changes, muscle mass, and true kidney-function change may all contribute.
Longitudinal model
Fit change through all observations rather than using only two endpoints
Observations are placed at equal intervals across the entered follow-up duration. Ordinary least squares estimates the monthly slope; the result is annualized. Residual standard deviation describes scatter around the fitted path.
Detailed calculation process and general formulas
t_i = i x months / 5b_month = sum((t_i-t_bar)(G_i-G_bar)) / sum((t_i-t_bar)^2)b_year = 12 x b_monthGhat_i = a + b_month x t_iSD_res = sqrt(sum((G_i-Ghat_i)^2) / 6)Symbols, meanings, and units
- t_i
- time of observation i from baselinemonths
- G_i
- observed eGFRmL/min/1.73 m2
- b_year
- annualized fitted slopeeGFR units/year
- Ghat_i
- fitted eGFRmL/min/1.73 m2
- SD_res
- root-mean-square residual scattereGFR units
Trend interpretation
Read direction, variability, and albuminuria together
No one metric replaces clinical review.
Direction
—The annualized fitted slope summarizes the series direction.
Scatter
—Residual variability shows how tightly observations follow that direction.
Damage context
—Urine ACR adds information not contained in eGFR alone.
Decision takeaway: Investigate a persistent trajectory; do not explain it from the slope alone.
Applied decisions
Patterns that endpoint change can hide
One temporary low result
Five values cluster while one falls during acute illness.
What the result clarifies: Residual scatter rises and the raw point remains visible instead of redefining the whole trend.
Small consistent decline
Every observation falls slightly across thirty months.
What the result clarifies: A modest endpoint change can still produce a coherent negative slope.
Worked default scenario
Current-input substitution and reconciliation
Method references
Evidence used to frame this specific model
Scope and limitations
This calculator describes entered results and cannot diagnose CKD progression or acute kidney injury. Unequal real testing intervals should be modeled with exact dates in clinical software rather than the equal-spacing approximation used here.
Kidney Function Trend Calculator | eGFR Slope and Variability FAQ
Why use six observations?
Multiple results make direction and scatter more visible than a two-point comparison.
Is the slope a forecast?
No. It summarizes the entered past interval and need not continue.
Why include urine ACR?
Albuminuria provides kidney-damage and risk context that eGFR alone does not capture.
Can different eGFR equations be mixed?
Equation changes can create artificial shifts; use comparable methods or annotate the transition.