R/calc_egfr_cystatin.R

In InsightRX/clinPK: Clinical Pharmacokinetics Toolkit

#' Calculate eGFR based on Cystatin C measurements
#'
#' @param method eGFR estimation method, choose from `grubb`, `larsson`, `hoek`
#' @param cystatin serum cystatin concentration (mg/L)
#' @param cystatin_unit, only `mg/L` available
#' @param unit_out eGFR output unit, choose from `ml/min`, `ml/hr`, `l/min`, `l/hr`
#' @examples
#' calc_egfr_cystatin(1.0)
#' calc_egfr_cystatin(1.0, method = "larsson")
#' calc_egfr_cystatin(1.0, unit_out = "l/hr")
#' @export
calc_egfr_cystatin <- function (
  cystatin = NULL,
  cystatin_unit = "mg/L",
  method = c("grubb", "larsson", "hoek"),
  unit_out = c("ml/min", "ml/hr", "l/min", "l/hr", "ml/min/1.73m2")
) {
  method <- gsub("-", "_", tolower(method))
  unit_out <- tolower(unit_out)
  method <- match.arg(method)
  unit_out <- match.arg(unit_out)
  crcl <- NULL
  unit <- cystatin_unit
  if(method == "grubb") {
    crcl <- 83.93 * cystatin^(-1.676)
    if(unit_out == "ml/min/1.73m2") {
      stop("Output unit not supported for this method.")
    }
  }
  if(method == "larsson") {
    crcl <- 77.239 * cystatin^(-1.2623)
    if(unit_out == "ml/min/1.73m2") {
      stop("Output unit not supported for this method.")
    }
  }
  if(method == "hoek") {
    crcl <- -4.32 + (80.35/cystatin)
    if(tolower(unit_out) != "ml/min/1.73m2") {
      stop("For Hoek method, the `unit_out` needs to be mL/min/1.73m2.")
    }
  }
  if (length(grep("^l/min", tolower(unit_out))) > 0) {
    crcl <- crcl / 1000
  }
  if (length(grep("^l/hr", tolower(unit_out))) > 0) {
    crcl <- crcl * 60 / 1000
  }
  if (length(grep("^ml/hr", tolower(unit_out))) > 0) {
    crcl <- crcl * 60
  }
  return(list(
    value = crcl,
    unit = unit_out
  ))
}