sitar (version 1.4.0)

ukwhoterm: UK-WHO growth reference omitting preterm data

Description

The UK-WHO growth reference for height, weight, BMI and head circumference (see Wright et al 2010), fitted by the LMS method and summarised by values of L, M and S by sex and postnatal age from term birth (see Details) to 20 years.

Usage

ukwhoterm

Format

A tibble with 512 observations on the following 15 variables:

years

numeric vector - postnatal age in years

L.ht

numeric vector

M.ht

numeric vector

S.ht

numeric vector

L.wt

numeric vector

M.wt

numeric vector

S.wt

numeric vector

L.bmi

numeric vector

M.bmi

numeric vector

S.bmi

numeric vector

L.head

numeric vector

M.head

numeric vector

S.head

numeric vector

origin

two-level factor indicating the provenance of the data, with levels British1990 and WHO2006

sex

two-level factor with level 1 male and level 2 female

Details

The growth reference combines term birth data from the British 1990 growth reference (Cole et al 2011), the WHO growth standard from 2 postnatal weeks to 4 years, and the British 1990 reference from 4 to 20 years.

Age is measured in years, and term birth corresponds to ages between 37 and 42 weeks gestation, where 40 weeks gestation is 0 years. The conversion is: years = (weeks - 40) * 7 / 365.25.

The L, M and S values for each measurement correspond respectively to the Box-Cox power, median and coefficient of variation of the distribution by age and sex (Cole & Green 1992). The measurement short names and units (see LMS2z) are as follows: height (ht, cm), weight (wt, kg), BMI (bmi, kg/m2) and head circumference (head, cm).

References

Cole TJ, Green PJ. Smoothing reference centile curves: the LMS method and penalized likelihood. Stat Med 1992;11:1305-19.

Cole TJ, Williams AF, Wright CM, et al. Revised birth centiles for weight, length and head circumference in the UK-WHO growth charts. Ann Hum Biol 2011;38:7-11.

Wright CM, Williams AF, Elliman D, et al. Using the new UK-WHO growth charts. BMJ 2010;340:c1140.

Examples

data(ukwhoterm)
## calculate median weight (kg) in girls from 0 to 10 years
v <- LMS2z(x = 0:10, y = 0, sex = 2, measure = 'wt',
  ref = 'ukwhoterm', toz = FALSE)
setNames(v, 0:10)