Get size-for-gestational age categories using multiple vectors and the INTERGROWTH-21st weight-for-gestational age standard

Get size-for-gestational age categories using multiple vectors and the INTERGROWTH-21^st weight-for-gestational age standard

Usage

compute_sfga(weight_kg, gest_days, sex, severe = FALSE)

Arguments

weight_kg: Numeric vector of length one or more with weight value(s) 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: Numeric vector of length one or more with gestational ages in days. Classifications can only be computed when gest_days is between 168 and 300, as these are the limits of the INTERGROWTH-21^st Newborn Size standards (including the Very Preterm standards). By default, gigs will warn you about elements of gest_days which are either outside these bounds, are NA, or are Inf. You can customise this behaviour using the GIGS package-level options.
sex: Character vector of length one or more with sex(es), either "M" (male) or "F" (female). This argument is case-sensitive. By default, gigs will replace elements of sex which are not "M" or "F" with NA and warn you. You can customise this behaviour using the GIGS package-level options.
severe: A single logical value specifying whether to categorise SGA values below the third centile (0.03) as "SGA(<3)". Default = FALSE.

Value

An object of class factor with the same length as the longest input vector, containing size-for-GA classifications. If severe = FALSE, levels are c("SGA", "AGA", "LGA"). If severe = TRUE, levels are c("SGA(<3)", "SGA", "AGA", "LGA"). By default, gigs will inform you this object contains unused factor levels. You can change this behaviour using the GIGS package-level option .gigs_options$handle_unused_levels.

Details

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

Category	Factor level	Centile 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

Input vectors are recycled by vctrs::vec_recycle_common(), and must adhere to the vctrs recycling rules.

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.

Examples

# By default, does not differentiate between p < 0.03 and p < 0.10
compute_sfga(
  weight_kg = c(2.2, 2.5, 3.3, 4.0),
  gest_days = 266:269,
  sex = c("F", "M", "F", "M")
)
#> [1] SGA SGA AGA LGA
#> Levels: SGA AGA LGA

# With severe = TRUE, highlights p < 0.03
compute_sfga(
  weight_kg = c(2.2, 2.5, 3.3, 4.0),
  gest_days = 266:269,
  sex = c("F", "M", "F", "M"),
  severe = TRUE
)
#> [1] SGA(<3) SGA     AGA     LGA    
#> Levels: SGA(<3) SGA AGA LGA