BIS (Berlin Initiative Study)

Creatinine-based BIS1 equation for adults aged 70 years or older

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

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

Formula

eGFR=3736×SCr−0.87×age−0.95×0.82[female]\text{eGFR} = 3736 \times \text{SCr}^{-0.87} \times \text{age}^{-0.95} \times 0.82^{[\text{female}]}

As text: eGFR = 3736 × SCr^(-0.87) × age^(-0.95) × (0.82 if female)

Constants

SymbolMeaningValue
3736Base coefficient
−0.87Creatinine exponent
−0.95Age exponent
Sex factorSex-dependent multiplier
Female: 0.82
Male: 1.00
ScrS_{cr}Serum creatinine (input)mg/dL
AgePatient age (input)years

How it was developed

Developed in 570 adults aged 70 years or older from the Berlin Initiative Study, a population-based cohort of Berlin residents insured by AOK Nordost, a statutory health insurer. GFR was measured as plasma iohexol clearance; the equation was built in a 285-person learning sample, internally validated in the other 285, and its final coefficients fitted on all 570.

Clinical notes

  • Creatinine-only version (BIS1); the paper's BIS2 also uses cystatin C
  • Derived with IDMS-traceable enzymatic creatinine (Roche CREA Plus)

Limitations

  • Developed in white participants only; other ethnicities not studied
  • Developed in normal to moderately reduced kidney function, not severe impairment
  • 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
  2. Ebert N, Jakob O, Gaedeke J, et al. Prevalence of reduced kidney function and albuminuria in older adults: the Berlin Initiative Study. Nephrol Dial Transplant. 2017;32(6):997-1005. doi:10.1093/ndt/gfw079

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