BIS Creatinine-Cystatin C

Berlin Initiative Study

Creatinine and cystatin C BIS2 equation for adults aged 70 years or older

Biomarkers
Creatinine + cystatin C
Validated for
70+ years
Inputs
Age, Sex, Creatinine, Cystatin C
Reports
mL/min/1.73 m²
Published
2012

The eGFR guide explains which equation the calculator suggests and indexed and absolute GFR.

Formula

eGFR=767×SCysC−0.61×SCr−0.40×age−0.57×0.87[female]\text{eGFR} = 767 \times \text{SCysC}^{-0.61} \times \text{SCr}^{-0.40} \times \text{age}^{-0.57} \times 0.87^{[\text{female}]}

As text: eGFR = 767 × SCysC^(-0.61) × SCr^(-0.40) × age^(-0.57) × (0.87 if female)

Constants

SymbolMeaningValue
767Base coefficient
−0.61Cystatin C exponent
−0.40Creatinine exponent
−0.57Age exponent
Sex factorSex-dependent multiplier
Female: 0.87
Male: 1.00
ScysCS_{cysC}Serum cystatin C (input)mg/L
ScrS_{cr}Serum creatinine (input)mg/dL
AgePatient age (input)years

How it was developed

Developed alongside BIS1 in the same 570 adults aged 70 or older, a non-random subsample of the Berlin Initiative Study, a population-based cohort of Berlin residents insured by AOK Nordost. GFR was measured as plasma iohexol clearance; built in a 285-person learning sample, internally validated in the other 285, with final coefficients fitted on all 570.

Clinical notes

  • Published as BIS2; the BIS equation is the paper's creatinine-only version (BIS1)
  • Derived with IDMS-traceable enzymatic creatinine (Roche CREA Plus) and ERM-DA471/IFCC-standardized cystatin C (Siemens BN ProSpec)

Limitations

  • Developed in white participants only; other ethnicities not studied
  • Developed mostly in normal to moderately reduced kidney function; only 17 of 570 had measured GFR below 30
  • People on dialysis or with a kidney transplant were excluded

References

  1. Schaeffner ES, Ebert N, Delanaye P, et al. Two novel equations to estimate kidney function in persons aged 70 years or older. Ann Intern Med. 2012;157(7):471-481. doi:10.7326/0003-4819-157-7-201210020-00003

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