WHOanthro

GENERATE SEX- AND AGE (or LENGTH)-STANDARDIZED WEIGHT, HEIGHT/LENGTH, AND BMI METRICS FROM THE WHO GROWTH CHARTS

Has a single function, 'whoanthro'. Requires the package data.table to be installed; library(whoanthro) will also attach data.table. These calculations are similar to those at https://www.cdc.gov/nccdphp/dnpao/growthcharts/resources/sas-who.htm.

Although there is a CRAN package, anthro, for generating z-scores based on the WHO growth charts, whoanthro is much faster and combines your original data with the calculated z-scores and percentiles. In contrast, anthro::anthro_zscores outputs only the calculated z-scores forcing you to cbind them with your original data (and hope that the row order is correct).

To install package:

install.packages('https://raw.github.com/CDC-DNPAO/WHOAnthro/master/whoanthro_0.1.1.tar.gz', type='source', repos=NULL)

To use package:

whoanthro(data, agedays = age_in_days, wt = weight_kg, lenhei = length or height, headc=head_circumference, bmi = bmi)

If a variable (e.g, head circumference) is missing for all records, specify as '= NA' in function. So, whoanthro(data, agedays, wt, lenhei, headc=NA, bmi)

Do NOT put arguments in quotation marks, such as whoanthro(data,'agedays','wt','lenhei', 'headc','bmi'). Use: whocanthro(data, agedays, wt, lenhei, headc)

Expects 'sex' to be a variable in the dataset. Can be coded as either 'boys/girls' or 'male/female', or '1/2'.
Character values can be upper or lower case; only the first character is considered.

Weight is in kg, and lenhei is length or height in cm. BMI is kg/m^2.

If age is in completed number of months, multiply by 30.4375 and add 15.219 (1/2 of 30.4375). Then take the floor of this value. Age in the WHO reference data is given as 0 to 1826 days.

Returns a data.table containing the original data and various weight, height, and BMI metrics. Can convert this to a data frame with 'setDF(output_data)'.

Variables in output:

waz: weight-for-sex/age z-score

lhaz: length (or height) for sex/age z-score

wflz: weight-for-length for sex z-score

bmiz: BMI-for-sex/age z-score

headcz: head circumference for sex/age z-score

References:

World Health Organization. Department of Nutrition for Health and Development. WHO Child Growth Standards. Length/height-for-age, weight-for-age, weight-for-length, weight-for-height, and body mass index-for-age. Methods and Development [Internet]. Geneva; 2006.
http://www.who.int/childgrowth/standards/technical_report/en/

Author: D Freedman

Reference data are the EXPANDED LMS data tables (at bottom of page) files at

https://www.who.int/tools/child-growth-standards/standards/weight-for-length-height

https://www.who.int/tools/child-growth-standards/standards/length-height-for-age

https://www.who.int/tools/child-growth-standards/standards/weight-for-age

https://www.who.int/toolkits/child-growth-standards/standards/body-mass-index-for-age-bmi-for-age

https://www.who.int/tools/child-growth-standards/standards/head-circumference-for-age

Examples

nhanes # NHANES data (2015/16 and 2017/18)

data = whoanthro(nhanes, agedays, wt, lenhei, headc, bmi) round(data,2)

if head circumference, for example, is not in dataset:

data = whoanthro(nhanes, agedays, wt, lenhei, bmi=bmi)

data = whoanthro(nhanes, agedays, wt, lenhei, , bmi)

round(data, 2)