What is the Kidney Failure Risk Equation?
The Kidney Failure Risk Equation (KFRE), also called the Tangri kidney failure risk calculator, estimates the probability of treated kidney failure — dialysis or kidney transplant — within 2 years or 5 years in adults with CKD stages 3–5. The 4-variable KFRE uses age, sex, eGFR and urine albumin-to-creatinine ratio (UACR). The 8-variable form adds serum albumin, phosphate, bicarbonate and calcium.
How KFRE inputs combine
Age, sex, eGFR and UACR feed the Cox model to yield treated kidney failure probability.
Nephrology referral thresholds
5-year KFRE guides CKD progression counseling and referral (NICE NG203).
| 5-year KFRE | Action |
|---|---|
| < 3% | Routine CKD monitoring |
| 3–5% | Shared decision-making |
| ≥ 5% | Consider nephrology referral |
| ≥ 15% | High risk — urgent co-management |
How is kidney failure risk calculated?
- Confirm CKD stage 3–5 context (eGFR < 60 with stability over months, not AKI).
- Enter age, sex, region, eGFR and spot urine ACR in mg/g.
- Optionally add albumin, phosphate, bicarbonate and calcium for the 8-variable model.
- Read 2-year and 5-year probability of dialysis or transplant.
KFRE 4-variable formula
Linear predictor (PI)
PI = −0.2201(age/10 − 7.036) + 0.2467(male − 0.5642) − 0.5567(eGFR/5 − 7.222) + 0.4510(ln UACR − 5.137)
Risk
Risk = 1 − S0exp(PI) · S0(2y NA) = 0.975 · S0(5y NA) = 0.924
UACR is in mg/g. Non–North American cohorts use S0(2y) = 0.9832 and S0(5y) = 0.9365.
8-variable KFRE
When serum albumin, phosphate, bicarbonate and calcium are available, the 8-variable kidney failure risk equation refines discrimination. Coefficients are centred at albumin 3.997 g/dL, phosphate 3.916 mg/dL, bicarbonate 25.57 mEq/L and calcium 9.355 mg/dL.
What does KFRE percentage mean?
A 5-year kidney failure risk calculator result of 12% means an estimated 12 in 100 similar patients would start dialysis or receive a transplant within five years. It is not mortality risk or all-cause hospitalization. Use it with blood pressure, diabetes control and patient preferences.
Is my CKD going to progress to kidney failure?
Progression depends on eGFR slope, albuminuria, blood pressure, diabetes, ACEi/ARB use and access to care. KFRE vs eGFR alone: adding UACR captures proteinuria risk that eGFR alone misses. A patient with eGFR 45 and UACR 500 mg/g has higher risk than eGFR 45 with UACR 20 mg/g.
When to see a nephrologist for CKD
NICE and KDIGO support nephrology referral risk calculator thresholds: 5-year KFRE ≥ 5%, rapidly falling eGFR, resistant hypertension, or persistent albuminuria A2/A3. The CKD stage 3 to 5 risk calculator is most validated in referred CKD populations; recalibrate expectations in primary care if your region differs.
4-variable vs 8-variable KFRE
The KFRE 4 variable calculator is sufficient for most clinic visits because eGFR and UACR are routine. The KFRE 8 variable calculator adds value when recent metabolic labs are already drawn — for example in advanced CKD clinics. This page shows both when extended labs are entered.
Calculation example
Male, 68 years, North America, eGFR 28, UACR 450 mg/g (4-variable):
- 2-year treated kidney failure risk ≈ 10.7%
- 5-year risk ≈ 29.9% — elevated risk band; nephrology discussion recommended
With the same case plus albumin 38 g/L, phosphate 4.8 mg/dL, bicarbonate 22 mEq/L and calcium 9.1 mg/dL (8-variable), 5-year risk ≈ 37.2%. Press Example to load all values.
Kidney Failure Risk FAQ
What is the Kidney Failure Risk Equation?
The Tangri KFRE predicts dialysis or transplant within 2 or 5 years using age, sex, eGFR and UACR in CKD stages 3–5.
How is kidney failure risk calculated?
A Cox model: Risk = 1 − S₀^exp(PI). PI combines centred age, sex, eGFR and natural log of UACR. Optional labs extend to 8 variables.
What does KFRE percentage mean?
Probability of treated kidney failure (dialysis or transplant), not death. Expressed as percent over 2 or 5 years.
Is my CKD going to progress to kidney failure?
KFRE quantifies risk but cannot guarantee individual outcomes. Trends in eGFR, UACR and comorbidities matter alongside the score.
When to see a nephrologist for CKD?
Consider referral at 5-year KFRE ≥ 5%, rapid eGFR decline, or ACR ≥ 300 mg/g with management challenges.
5 percent kidney function life expectancy?
Life expectancy at very low eGFR depends on age, comorbidities and treatment choices. KFRE estimates treatment initiation, not survival — discuss goals of care with your team.
KFRE vs eGFR alone
UACR substantially changes risk at the same eGFR. KFRE is validated to outperform eGFR-only models for predicting kidney replacement therapy.
4-variable vs 8-variable KFRE
Use 4-variable in most settings. 8-variable may improve accuracy when metabolic labs are available; both are shown here when complete.
Risk of dialysis calculator vs transplant
KFRE combines both modalities as “treated kidney failure” — the composite endpoint used in Tangri derivation cohorts.
ESRD risk calculator — same as KFRE?
Yes. ESRD risk calculator, kidney disease risk assessment tool and KFRE refer to the same Tangri equations in most clinical contexts.
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User Reviews
4.9 / 5 from 3 recent users of this KFRE calculator
Region toggle and 4/8-variable logic match what we use on MDCalc. Referral band is clear for clinic letters.
Albumin g/L toggle and calcium mmol/L conversion work correctly. Side-by-side 4-var when 8-var runs.
Visual risk spectrum helps explain progression to patients. Example case is realistic for G4 CKD.
Related tools: eGFR calculator, MDRD GFR calculator, creatinine clearance calculator, and BUN creatinine ratio calculator.