Leptin SDS

In childsds: Data and Methods Around Reference Values in Pediatrics

knitr::opts_chunk$set(
  collapse = TRUE,
  comment = "#>"
)

library(childsds)
library(dplyr)
data(leptin.ref)

Children: Age- and BMI-SDS-adjusted Leptin-SDS

For children and adolescents up to an age of 18.5 years, leptin standard deviation scores will be calclated based on age on years and BMI-SDS. BMI-SDS via the x2= argument to the sds_2d() function.

Besides, the sds_2d() function takes the leptin value (value=), sex (sex=) and age (age=) as arguments. These values have to be given as vectors of the same length. In addition, it needs a reference object (in our case ref=leptin.ref) and the item (item=). For children younger than 6, the item is 'leptin_until6', for children between 6 and 18, it is 'leptin_6to18'. The function returns a numeric vector of the same length containing leptin-SDS (type="SDS") or leptin percentiles (type="perc").

A single value

sds_2d(value = 20, age = 10, x2 = 1, sex = "male", item = "leptin_until6", ref = leptin.ref)

Within a data set

Create a sample data set

df <- data.frame(age = seq(0.5, 6.5, by = 1),
                 sex = sample(c("m","f"),7, replace = T),
                 bmisds = rnorm(7),
                 leptin = runif(7, min = 0.01, max = 5))
df

Calculate Leptin-SDS

df$leptin_sds <- sds_2d(value = df$leptin,
                       age = df$age,
                       x2 = df$bmisds,
                       sex = df$sex, male = "m", female = "f",
                       item = "leptin_until6",
                       ref = leptin.ref)
df

Children: Tanner Stage and BMI-SDS dependent SDS values

For SDS adjusted for pubertal stage, you have to use the function sds_pub2d(). Again, the leptin value (value=), the Tanner stage (1-5, pubstat=), the BMI-SDS (x2=) and the sex (sex=) has to be given to the function as vectors of the same length. The ref object is still leptin.ref and the item=lep_pub. The reference values are valid for the age range 6-18.

A single value

sds_pub2d(value = 20,
          pubstat = 2,
          x2 = 1,
          sex = "male",
          item = "lep_pub", ref = leptin.ref)

Create a sample data set

df <- data.frame(age = seq(0.5, 6.5, by = 1),
                 sex = sample(c("m","f"),7, replace = T),
                 bmisds = rnorm(7),
                 leptin = runif(7, min = 0.01, max = 5))
df

Calculate Leptin-SDS

df$leptin_sds <- sds_2d(value = df$leptin,
                       age = df$age,
                       x2 = df$bmisds,
                       sex = df$sex, male = "m", female = "f",
                       item = "leptin_until6",
                       ref = leptin.ref)
df

Calculate Leptin-percentiles

df$leptin_perc <- sds_2d(value = df$leptin,
                       age = df$age,
                       x2 = df$bmisds,
                       sex = df$sex, male = "m", female = "f",
                       item = "leptin_until6",
                       type = "perc",
                       ref = leptin.ref)
df

Adults: Age- and BMI-adjusted Leptin-SDS

For adults until 80 years, leptin standard deviation scores will be calclated based on age on years and BMI. BMI is passed to the sds_2d() function via the x2= argument.

Besides, the sds_2d() function takes the leptin value (value=), sex (sex=) and age (age=) as arguments. These values have to be given as vectors of the same length. In addition, it needs a reference object (in our case ref=leptin.ref) and the item (item=). For adults, it is 'lep_bmi'. The function returns a numeric vector of the same length containing leptin-SDS (type="SDS") or leptin percentiles (type="perc").

A single value

sds_2d(value = 20, age = 20, x2 = 25, sex = "male", item = "lep_bmi", ref = leptin.ref)

Within a data set

Create a sample data set

df <- data.frame(age = seq(20, 80, by = 10),
                 sex = sample(c("M","F"),7, replace = T),
                 bmi = runif(7, 20, 40),
                 leptin = runif(7, min = 0.01, max = 20))
df

Calculate Leptin-SDS

df$leptin_sds <- sds_2d(value = df$leptin,
                       age = df$age,
                       x2 = df$bmi,
                       sex = df$sex, male = "M", female = "F",
                       item = "lep_bmi",
                       ref = leptin.ref)
df

childsds documentation built on April 4, 2025, 1:49 a.m.