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Assess Fetal, Newborn, and Child Growth with International Standards

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Version information:

• Package: gigs
• Version: 0.1.8
• Generated: 2024-11-21T17:32:25
• Author(s): Bartosz Jablonski ([email protected]), Simon Parker ([email protected]), Linda Vesel, Eric Ohuma ([email protected])
• Maintainer(s): Bartosz Jablonski ([email protected])
• License: GNU General Public License v3.0
• File SHA256: F*153695E7C4F007D2BFF34ACF7F666D95150F52E27ADA710EFEC8CD8FE2F804D0 for this version
• Content SHA256: C*C6B2B9B3B715F6D4CF01316EFF20F327394FC8F8D3B1CE47DFCB99BA3F6F778E for this version

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The gigs package, version: 0.1.8;

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gigs SAS Package

Overview

Produced as part of the Guidance for International Growth Standards project at the London School of Hygiene & Tropical Medicine, gigs provides a single, simple interface for working with the WHO Child Growth standards and outputs from the INTERGROWTH-21^st project. You will find functions for converting from anthropometric measures (e.g. weight or length) to z-scores and centiles, and the inverse. Also included are functions for classifying newborn and infant growth according to literature-based cut-offs.

gigs is of use to anyone interested in fetal and child growth, including child health researchers, policymakers, and clinicians. This package is best suited to growth data where the gestational age (GA) of each child is known, as the use of the growth standards included in gigs is GA-dependent. We recommend you check out the available standards section to see if your anthropometric measurements can be converted to z-scores/centiles by gigs. We recommend using gigs to generate continuous or categorical measures of fetal/newborn/child growth, which can then be used in downstream analyses.

Installation

Installing the SAS packages framework

gigs works with the SAS Packages Framework (SPF), so installing gigs requires that the SPF is installed. First, create a directory where the SPF and packages will be stored. This can be at any directory you choose, for example:

• D:\SAS_Packages
• /home/myuser/myPackages

SPF is designed in such a way that this directory you've made must be refered to by fileref packages. In your SAS session (preferably at the beginning), you should run the following code:

filename packages "/path/to/packages/directory";

Installing an SPF package, "in a nutshell", means copying SPFinit.sas (from packagename.zip) file into the packages directory. This can be done automatically or manually.

Installing gigs - automatic

To install gigs automatically, your SAS session must have access to the internet.

The following code will install the SAS Packages Framework, gigs, and macroArray (required for gigs to work). You only need to execute this code once:

filename packages "/path/to/packages/directory";
filename SPFinit url 
 "https://raw.githubusercontent.com/yabwon/SAS_PACKAGES/main/SPF/SPFinit.sas";      
%include SPFinit; 

%installPackage(SPFinit gigs macroArray)

filename SPFinit clear;

After running this code, check the log to see if the process was successful.

Installing gigs - manual

If your SAS session does not have access to the internet but you can copy files manually to your packages directory, you can install gigs like so:

• Download SPFinit.sas from here
• Download gigs.zip from here
• Download macroarray.zip from here

Once downloaded, copy these files manually to your SAS packages directory.

Using gigs in a SAS session

To use gigs in a new SAS session, you must enable the SAS Packages Framework, then load gigs with %loadPackage:

filename packages "/path/to/packages/directory";
%include packages(SPFinit.sas);
%loadPackage(gigs)

The macroArray package will be loaded automatically when gigs is loaded.

If using gigs often in your work, the most convenient/practical way to load gigs is to put those three lines of code in your autoexec.sas file.

Links to SAS Package Framework materials

The SAS Packages Framework (SPF)

Location of the SAS Packages Repository

Workshop materials

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Documentation

Package Documentation

Introductory Examples

Rationale + terminology

When working with growth measurements from individual children, it is helpful to compare those measurements to a growth standard, which represents average growth for an population of children. This allows assessment of individual growth - for example, that a baby was born small, but later caught up to its peers in size. It also allows you to compare measurements from different children.

These standards of growth can be made in different ways, but the best studies utilise international samples made of up thousands of healthy fetuses, newborns, or children. In gigs, you’ll find different international growth standards, allowing you to compare growth measures from children with different ages, weights, heights, and more.

In general, you’ll use gigs to transform raw growth measures to z-scores or centiles. Z-scores and centiles represent the location of a measurement within a normal distribution of values, such that:

• A z-score is the number of standard deviations from the mean for a given anthropometric measurement (e.g. height or weight).
• A centile represents the proportion of measurements in some distribution which we would expect to be lower than a measurement we’ve taken. In gigs, these are represented as a value between 0 and 1. For example, 0.5 corresponds to the 50^th centile (i.e. the mean), whereas 0.75 corresponds to the 75^th centile.

In growth data, z-scores and centiles represent the size a fetus, newborn, or child relative to its peers. Size here is considered relative to a standardising variable, which is usually age but could also be another variable such as their length. By tracking a child’s relative size as they grow, you can see if they are achieving their growth potential or not. If not, this may indicate underlying issues such as ill health or undernutrition.

Classification functions

gigs includes a number of functions which permit fast identification of at-risk infants through classification of suboptimal growth. The cut-offs used are sourced from research literature; you can check the function documentation to see these sources.

Available international growth standards

gigs facilitates the proper use of international growth standards, which are growth charts developed using international samples of healthy singleton children born to mothers that had their health needs met during pregnancy. They represent an international standard of 'optimal' growth. gigs implements international growth standards from the WHO and INTERGROWTH-21^st project:

• ig_nbs - INTERGROWTH-21^st Newborn Size standards (including very preterm)

  Component standards

  Acronym	Description	Unit	gest_days range
  wfga	weight-for-GA	kg	168 to 300 days
  lfga	length-for-GA	cm	168 to 300 days
  hcfga	head circumference-for-GA	cm	168 to 300 days
  wlrfga	weight-to-length ratio-for-GA	kg/cm	168 to 300 days
  ffmfga	fat-free mass-for-GA	kg	266 to 294 days
  bfpfga	body fat percentage-for-GA	%	266 to 294 days
  fmfga	fat mass-for-GA	kg	266 to 294 days

• ig_png - INTERGROWTH-21^st Postnatal Growth of Preterm Infants standards

  Component standards

  Acronym	Description	Unit	x range
  wfa	weight-for-age	kg	27 to ≤64 exact weeks
  lfa	length-for-age	cm	27 to ≤64 exact weeks
  hcfa	head circumference-for-age	cm	27 to ≤64 exact weeks
  wfl	weight-for-length	kg	35 to 65 cm

• ig_fet - INTERGROWTH-21^st Fetal standards

  Component standards

  Acronym	Description	Unit	x range
  hcfga	head circumference-for-GA	mm	98 to 280 days
  bpdfga	biparietal diameter-for-GA	mm	98 to 280 days
  acfga	abdominal circumference-for-GA	mm	98 to 280 days
  flfga	femur length-for-GA	mm	98 to 280 days
  ofdfga	occipito-frontal diameter for-GA	mm	98 to 280 days
  efwfga	estimated fetal weight-for-GA	g	154 to 280 days
  sfhfga	symphisis-fundal height-for-GA	mm	112 to 294 days
  crlfga	crown-rump length-for-GA	mm	58 to 105 days
  gafcrl	GA-for-crown-rump length	days	15 to 95 mm
  gwgfga	gestational weight gain-for-GA	kg	98 to 280 days
  pifga	pulsatility index-for-GA		168 to 280 days
  rifga	resistance index-for-GA		168 to 280 days
  sdrfga	systolic/diastolic ratio-for-GA		168 to 280 days
  tcdfga	transcerebellar diameter-for-GA	mm	98 to 280 days
  tcdfga	GA-for-transcerebellar diameter	mm	98 to 280 days
  poffga	parietal-occipital fissure-for-GA	mm	105 to 252 days
  sffga	Sylvian fissue-for-GA	mm	105 to 252 days
  avfga	anterior horn of the lateral ventricle-for-GA	mm	105 to 252 days
  pvfga	atrium of the posterior horn of the lateral ventricle-for-GA	mm	105 to 252 days
  cmfga	cisterna magna-for-GA	mm	105 to 252 days
  hefwfga	Hadlock estimated fetal weight-for-GA	g	126 to 287 days

• who_gs - WHO Child Growth Standards for term infants

  Component standards

  Acronym	Description	Unit	x range
  wfa	weight-for-age	kg	0 to 1856 days
  bfa	BMI-for-age	kg/m2	0 to 1856 days
  lhfa	length/height-for-age	cm	0 to 1856 days
  hcfa	head circumference-for-age	cm	0 to 1856 days
  wfl	weight-for-height	kg	45 to 110 cm
  wfh	weight-for-length	kg	65 to 120 cm
  acfa	arm circumference-for-age	cm	91 to 1856 days
  ssfa	subscapular skinfold-for-age	mm	91 to 1856 days
  tsfa	triceps skinfold-for-age	mm	91 to 1856 days

Funding

Bill & Melinda Gates Foundation

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Required SAS Components:

• Base SAS Software

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Required SAS Packages:

• macroArray (1.2.6)

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SAS package generated by SAS Package Framework, version 20241102

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