Categorize Renal Function

This function categorizes renal function based on estimated glomerular filtration rate (eGFR), creatinine clearance, or other renal function estimators. It supports both clinical and regulatory categorization standards and can convert between absolute (mL/min) and relative (mL/min/1.73m²) units using body surface area.

Usage

rfc(
  estimator = NULL,
  bsa = NULL,
  category_standard = c("regulatory", "clinical"),
  absolute_units = NULL
)

Arguments

estimator

Numeric vector of renal function estimator values (eGFR, CrCL, etc.)

bsa

Numeric vector of body surface area in m² for unit conversion. Required when converting between absolute and relative units

category_standard

Character string specifying categorization standard: "regulatory" (default) or "clinical"

absolute_units

Logical indicating if estimator units are mL/min (TRUE) or mL/min/1.73m² (FALSE)

Value

Integer vector of renal impairment categories (1-4 for regulatory, 1-5 for clinical). Returns -999 for missing values. Includes a category_standard attribute indicating the source ("FDA" or "KDIGO").

Details

The function applies different categorization schemes based on the category_standard:

Regulatory categories (uses mL/min):

• 1: Normal: ≥90 mL/min

• 2: Mild impairment: 60-89 mL/min

• 3: Moderate impairment: 30-59 mL/min

• 4: Severe impairment: <30 mL/min

Clinical categories (uses mL/min/1.73m²):

• 1: Normal: ≥90 mL/min/1.73m²

• 2: Mild impairment: 60-89 mL/min/1.73m²

• 3: Moderate impairment: 30-59 mL/min/1.73m²

• 4: Severe impairment: 15-29 mL/min/1.73m²

• 5: End-stage: <15 mL/min/1.73m²

When unit conversion is required, the function uses:

• Absolute to relative: relative = 1.73 (absolute / bsa)

• Relative to absolute: absolute = relative (bsa / 1.73)

References

FDA Guidance for Industry: Pharmacokinetics in Patients with Impaired Renal Function. https://www.fda.gov/media/78573/download

KDIGO 2024 Clinical Practice Guideline for the Evaluation and Management of Chronic Kidney Disease. https://www.kidney-international.org/action/showPdf?pii=S0085-2538(23)00766-4

See also

egfr for calculating eGFR, crcl for creatinine clearance, bsa for body surface area calculation

Other renal_function: aegfr(), ckdepi_2009_egfr(), ckdepi_2021_egfr(), ckdepi_2021_egfr_cystatin(), crcl(), egfr(), mdrd_egfr(), schwartz_egfr()

Examples

# Regulatory categories with absolute units (creatinine clearance)
rfc(estimator = c(95, 75, 45, 25), absolute_units = TRUE)
#> [1] 1 2 3 4
#> attr(,"category_standard")
#> [1] "FDA"

# Clinical categories with relative units (eGFR)
rfc(
  estimator = c(95, 75, 45, 25, 10),
  absolute_units = FALSE,
  category_standard = "clinical"
)
#> [1] 1 2 3 4 5
#> attr(,"category_standard")
#> [1] "KDIGO"

# Convert relative eGFR to regulatory categories
rfc(
  estimator = 65,
  absolute_units = FALSE,
  bsa = 1.8
)
#> [1] 2
#> attr(,"category_standard")
#> [1] "FDA"

# Pipeline example with realistic data
df <- data.frame(
  ID = 1:4,
  SEX = c("F", "M", "F", "M"),
  AGE = c(65, 45, 70, 50),
  CREAT = c(1.2, 0.9, 1.5, 1.1),
  WEIGHT = c(70, 80, 60, 85),
  HEIGHT = c(165, 175, 160, 180),
  RACE = c("WHITE", "BLACK", "OTHER", "ASIAN")
)

library(dplyr)
df %>%
  mutate(
    BSA = bsa(WEIGHT, HEIGHT, method = "Dubois"),
    EGFR = egfr(is_female(SEX), is_black(RACE), AGE, CREAT),
    AEGFR = aegfr(EGFR, BSA),
    # Clinical categories using relative eGFR directly
    BRFC_CLINICAL = rfc(EGFR, category_standard = "clinical"),
    # Regulatory categories - convert relative eGFR to absolute
    BRFC_REGULATORY_REL = rfc(EGFR, BSA),
    # Regulatory categories - AEGFR already absolute
    BRFC_REGULATORY_ABS = rfc(AEGFR)
  )
#>   ID SEX AGE CREAT WEIGHT HEIGHT  RACE      BSA      EGFR     AEGFR
#> 1  1   F  65   1.2     70    165 WHITE 1.770960  50.23467  51.42405
#> 2  2   M  45   0.9     80    175 BLACK 1.956060 107.33541 121.36097
#> 3  3   F  70   1.5     60    160 OTHER 1.622063  37.25688  34.93236
#> 4  4   M  50   1.1     85    180 ASIAN 2.048528  81.78201  96.83973
#>   BRFC_CLINICAL BRFC_REGULATORY_REL BRFC_REGULATORY_ABS
#> 1             3                   3                   3
#> 2             1                   1                   1
#> 3             3                   3                   3
#> 4             2                   1                   1
df
#>   ID SEX AGE CREAT WEIGHT HEIGHT  RACE
#> 1  1   F  65   1.2     70    165 WHITE
#> 2  2   M  45   0.9     80    175 BLACK
#> 3  3   F  70   1.5     60    160 OTHER
#> 4  4   M  50   1.1     85    180 ASIAN