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Classify size-for-gestational age in data.frame-like objects with the INTERGROWTH-21st weight-for-gestational age standard

Source: R/growth_classify.R
classify_sfga.Rd

Classify size-for-gestational age in data.frame-like objects with the INTERGROWTH-21st weight-for-gestational age standard

Usage

classify_sfga(
  .data,
  weight_kg,
  gest_days,
  sex,
  .new = c("birthweight_centile", "sfga", "sfga_severe")
)

Arguments

.data

A data.frame-like tabular object with one or more rows. Must be permissible by checkmate::assert_data_frame(), so you can also supply a tibble, data.table, or similar.

weight_kg

<data-masking> The name of a column in .data which is a numeric vector of birth weight values in kg. It is assumed that weight measurements provided to this function are birth weights recorded <12 hours after an infant's birth.

gest_days

<data-masking> The name of a column in .data which is a numeric vector of gestational age(s) at birth in days between 168 and 300. By default, gigs will warn you about elements of this vector which are outside these bounds, are NA, or Inf. You can customise this behaviour using the GIGS package-level options.

sex

<data-masking> The name of a column in .data which is a case-sensitive character vector of sexes, either "M" (male) or "F" (female). By default, gigs will warn you if any elements of sex are not "M" or "F", or are missing (NA). You can customise this behaviour using the GIGS package-level options.

.new

A three-length character vector with names for the output columns. These inputs will be repaired if necessary using vctrs::vec_as_names(), which will print any changes to the console. If any elements in .new are the same as elements in colnames(.data), the function will throw an error. Default = c("birthweight_centile", "sfga", "sfga_severe").

Value

A tabular object of the same class that was provided as .data, with three new columns named according to .new. These columns will be (from left to right):

  • birthweight_centile - Numeric vector of birthweight centiles from the INTERGROWTH-21st Newborn Size standard for weight-for-GA

  • sfga - Factor of size-for-GA categories without severe small-for-GA classification

  • sfga_severe - Factor of size-for-GA categories with severe small-for-GA classification

Details

Cut-offs for size-for-gestational age categorisations are:

CategoryFactor levelCentile bounds
Severely small-for-GA"SGA(<3)"p < 0.03
Small-for-GA"SGA"p < 0.1
Appropriate-for-GA"AGA"0.1 =< p =< 0.9
Large-for-GA"LGA"p > 0.9

Note

Categorical (factor) columns produced here may contain unused factor levels. By default, gigs will inform you if these columns have unused factor levels. You can change this behaviour using the GIGS package-level option .gigs_options$handle_unused_levels.

References

WHO. Physical status: the use and interpretation of anthropometry. Report of a WHO Expert Committee. World Health Organisation Technical Report Series 1995, 854: 1–452

Royal College of Obstetricians and Gynaecologists. The Investigation and Management of the Small-for-Gestational-Age Fetus: Green-top Guideline No. 31. Technical report, Royal College of Obstetricians and Gynaecologists, London, 2013.

See also

See classify_svn() for size-for-GA classifications which are stratified by whether a newborn is term. See classify_growth() to run this analysis and others at the same time.

Examples

data <- data.frame(
 wt_kg = c(2.2, 2.5, 3.3, 4.0),
 gestage = 266:269,
 sex = c("F", "M", "F", "M")
)

data |>
  classify_sfga(weight_kg = wt_kg,
                gest_days = gestage,
                sex = sex)
#>   wt_kg gestage sex birthweight_centile sfga sfga_severe
#> 1   2.2     266   F          0.01890983  SGA     SGA(<3)
#> 2   2.5     267   M          0.06485308  SGA         SGA
#> 3   3.3     268   F          0.75655402  AGA         AGA
#> 4   4.0     269   M          0.97108564  LGA         LGA