Anthropometric Standardization (Growth Charts)

 

Menu location: Data_Transforming and Deriving_Anthropometric Standardization; Clinical Epidemiology_Growth Charts

 

This function provides standard deviation scores (z scores) for common anthropometric measures in children, such as height, weight, and BMI, with reference to British, US and WHO growth standards.

 

The method of standardisation is LMS (lambda, mu, sigma) of Cole et al. (1992) with extensions (World Health Organisation 2006, 2007; Vidmar et al. 2013).

 

You provide:

 

[* weight can be standardised for length or height as well as age: see reference standards below]

 

StatsDirect returns the z score for the measure, which is the number of standard deviations the child's measurement is from the average child of equivalent age (+ gestational age) and sex in the reference population.

 

The standard deviation score z ranges from -5 to +5 because StatsDirect considers more extreme values to be erroneous, so returns them as missing values.

 

In terms of percentiles: z = 0 is the 50th percentile, or exactly average; z = 1 would be the 84th percentile and z = -1 would be the 16th percentile. The percentile is calculated using the standard normal distribution function (lower tail), which is the proportion of normal children expected to have that measurement or a lower measurement.

 

For BMI, in addition to a z score, StatsDirect returns a category [G3 Thin = grade 3 thinness; G2 Thin = grade 2 thinness; G1 Thin = grade 1 thinness; Normal = normal weight; Overweight = overweight; Obese = obese]. The adult equivalent BMI cut-off levels for these categories are: <16 = G3 Thin; 16 to <17 = G2 Thin; 17 to <18.5 = G1 Thin; 18.5 to <25 = Normal; 25 to <30 = Overweight; >30 = Obese.

 

The growth reference standards included are:

 

British Growth Reference 1990: UK

Height/length (0-23 years)*

Weight (0-23 years)**

BMI (0-23 years)*

Head circumference (0-18 years for males, 0-17 years for females)**

Sitting height (0-23 years)

Leg length (0-23 years)

Waist circumference (3-17 years)

Body fat percentage (4.75-19.83 years)

 

[* can be adjusted for gestational age from 33 weeks; or ** 23 weeks]

 

Centres for Disease Control (CDC) 2000: US

Length (0-35.5 months)

Height (2-20 years)

Weight (0-20 years) or (45-103.5 cm length) or (77-121.5 cm height)

BMI (2-20 years)

Head circumference (0-36 months)

 

World Health Organisation (WHO) 2007: Term gestation

Height/length (0-19 years)

Weight (0-10 years) or (45-110 cm length) or 65-120 cm height)

BMI (0-19 years)

Head circumference (0-5 years)

Arm circumference (0.25-5 years)

Subscapular skin fold (0.25-5 years)

Triceps skin fold (0.25-5 years)

 

WHO 2007: Pre-term

Height/length (0-20 years)*

Weight (0-20 years)**

BMI (0.038-20 years)

Head circumference (0-18 years for males, 0-17 years for females)**

 

[* can be adjusted for gestational age from 25 weeks; or ** 23 weeks]

 

WHO 2009: Term

Height/length (0-20 years)*

Weight (0-20 years)*

BMI (0.038-20 years)

Head circumference (0-18 years for males, 0-17 years for females)*

 

[* can be adjusted for gestational age from 37 weeks]

 

Example

Test workbook (Other worksheet: BMI, Age (Years), Sex).

 

Selecting the British 1990 Growth Reference standard for the above gives:

 

BMI Age (Years) Sex Z BMI BMI Category
12.9836 13.23 M -3.92786 G3 Thin
16.6044 13.45 M -.9190669 Normal
16.3571 13.95 M -1.251696 G1 Thin
19.3618 13.66 F .0688321 Normal
19.9865 13.37 M .7128484 Normal
23.9573 13.91 M 1.752847 Overweight
25.6782 13.27 M 2.220984 Overweight
18.1122 13.39 M -.0810537 Normal
18.5931 13.35 F -.168254 Normal
31.8787 13.72 F 2.89563 Obese
18.5544 13.95 F -.3408737 Normal
21.7519 13.67 M 1.223346 Normal

 

 

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