Skip to contents

Estimate renal function using various equations

Source: R/PMaddCRCL.R
add_renal.Rd

[Stable]

Adds columns to PM_data object for creatinine clearance or estimated glomerular filtration rate (eGFR).

Creatinine clearance can be estimated by:

  • The Jelliffe equation for paired creatinines

  • The Cockcroft-Gault equation using a single creatinine.

eGFR can be estimated by:

  • The MDRD equation

  • The CKD-EPI equation

  • The Schwartz equation for children

Usage

add_renal(
  x,
  method,
  id = "id",
  wt = "wt",
  ht = "ht",
  male = "male",
  age = "age",
  black = "black",
  scr = "scr",
  bun = "bun",
  cysC = "cysC",
  SI = F
)

Arguments

x

A PM_data data object

method

A character vector defining the method to use. Options are

  • "jelliffe" or "jel"

  • "cockcroft-gault" or "cg"

  • "mdrd"

  • "ckd-epi" or "ckd"

  • "schwartz" For the fuller versions, Only the first 4 letters are required

id

A character vector with the name of the id column in x. The default is "id".

wt

A character vector with the name of the weight column in x. The default is "wt". Only required for "jelliffe" and "cockcroft-gault" methods. Values must be in kilograms.

ht

A character vector with the name of the height column in x. The default is "ht". Only required for the "schwartz" method. Values must be in meters

male

A character vector with the name of the column defining sex in x. Male should be 1 and female should be 0. The default is "male".

age

A character vector with the name of the age column in x. The default is "age". Values must be in years.

black

A character vector with the name of a column defining black race in x. Male should be 1 and female should be 0. The default is "male".

scr

A character vector with the name of the serum creatinine column in x. Default units are mg/dL, unless SI = TRUE below. The the default name is "scr".

bun

A character vector with the name of the blood urea nitrogen column in x. Default units are mg/dL, unless SI = TRUE below. Default name is "bun". Optional for the Schwartz method.

cysC

A character vector with the name of the cystatin C column in x. Units are always mg/L. Default is "cysC". Optional for the Schwartz method.

SI

Boolean value, if true, will expect serum creatinine to be in micromol/L and BUN reported as micromol/L of urea. Default is FALSE.

Value

A column added to the x data object with the name of the method used and calcuated values.

Details

Note: In all the equations below, age is in years, weight is in kilograms, height is in meters, and cystatin C (cysC) is in mg/L. Serum creatinine (Scr) is in mg/dL and blood urea nitrogen (BUN) is in mg/L. However, if SI = TRUE, then serum creatinine is in micromol/L and BUN is in micromol/L of urea.

Missing covariate values are interpolated using linear interpolation within each subject.

  • The Jelliffe equation depends on age, sex, weight, and serum creatinine. It uniquely uses two serum creatinine values separated by time to estimate changing renal function.

    • \(ESS = wt * (29.3 - (0.203 * age))\) for males

    • \(ESS = wt * (25.1 - (0.175 * age))\) for females

    • \(scrAve = (Scr1 + Scr2) / 2\)

    • \(ESS_cor = ESS * (1.035 - (0.0337 * scrAve))\)

    • \(E = ESS_cor - 4 * wt * (Scr2 - Scr1) / (time2 - time1)\)

    • \(CRCL = E / (14.4 * scrAve)\) in ml/min/1.73m^2

  • The Cockroft-Gault equation is a point estimate of creatinine clearance. It depends on the same variables as Jelliffe except it does not require paired creatinines.

    • \(CRCL = ((140 - age) * weight * K)/(72 * Scr)\)

    • \(K\) is 1 for males and 0.85 for females

  • The MDRD equation estimates GFR. It depends on age, sex, black race, and serum creatinine.

    • \(eGFR = 175 * (Scr)^{-1.154} * (age)^{-0.203}\)

    • Multiply by 1.212 if black.

  • The CKD-EPI equation estimates GFR. It depends on the same variables as MDRD, except black is no longer required in the 2021 version used here.

    • \(eGFR = 141 * min(Scr/k, 1)^a * max(Scr/k, 1)^{-1.209} * 0.993^{age}\)

    • Multiply by 1.1018 if female.

  • The Schwartz equation estimates GFR in children. The equation used depends on which covariates are included in the data.

    • height and serum creatinine: \(eGFR = 41.3 * height/scr\) (updated Scwartz equation)

    • height, serum creatinine, and cystatin C: \(eGFR = 41.6 * (height/scr)^{0.599} * (1.8/cysC)^{0.317}\) (Equation 1a)

    • height, serum creatinine, and BUN: \(eGFR = 40.7 * (height/scr)^{0.640} * (30/BUN)^{0.202}\) (Equation 1b)

    • height, serum creatinine, cystatin C, and BUN: \(eGFR = 41.1 * (height/scr)^{0.510} * (1.8/cysC)^{0.272} * (30/BUN)^{0.171}\) (Equation II)

    • height, serum creatinine, cystatin C, BUN, and male: \(eGFR = 39.1 * (height/scr)^{0.516} * (1.8/cysC)^{0.294} * (30/BUN)^{0.169} * 1.099^{male} * (height/1.4)^{1.88}\) (Equation III)

Discussion of the strengths and weaknesses of these equations are beyond the scope of this documentation.

Author

Michael Neely