What Is Normality? Flashcards
When is a child’s weight measured?
- 5 times during first year of life
- Possibly once during pre-school
- 1-2 times during school
When is a child’s head circumference measured?
- Twice in the first year of life, mainly to detect hydrocephalus
- Only measured at pre school and school ages to monitor existing problems.
When is a child’s length measured?
- During the first year of life this is only essential if there are concerns about faltering weight
- Only measured pre school and school age if child cannot stand
When is a child’s height measured?
- Not possible until age 2
- May be measured once at pre school age to calculate BMI
- 1-2 times at school age to calculate BMI
When is a child’s BMI measured?
- Not possible until age 2
2. 1-3 times at pre-school and school age to check for possible overweight/obesity issues
Describe how a child’s weight should be measured.
- Use clinical grade electronic scales
- Can be held in parents arms if child will not step on scales alone
- Babies should be weighed naked, toddlers in vest and pants and school children in light clothing
- No shoes should be worn
- No nappy for babies/toddlers
Describe how a child’s head circumference should be obtained.
- Use non elastic tape
- Wrap around widest part of the skull
- Measure three time or more (until 2 concordat readings)
Describe how a child’s length should be measured.
- Use a stiff or rigid length board, not a tape measure
2. 2 people (parent and healthcare professional needed - one to hold head, other to hold feet)
Describe how a child’s height should be measured.
- Using a rigid measure with T piece or stadiometer
- Head in Frankfurt plane (eyes level with top of ears)
- Standing straight with ankles, back and shoulders touching vertical plane of measure
- No shoes
- If necessary, stretch by holding hand under angle of jaw, then letting go before taking the measurement.
Apart from height, what other sorts of measurements are normally distributed in healthy individuals?
- Blood pressure
- Haemoglobin
- Plasma sodium
- Protein intake
In a graph showing the distribution of BMI in children, which statistics would be most useful to determine a ‘normal’ BMI?
- Median
- Inter quartile range - 25th to 75th percentile
- 2nd and 98th centile
How are growth charts made?
They are based on cross sectional individual samples of children of different ages and genders so you get a distribution of values.
Briefly describe a normal distribution pattern.
Most of the values would be in the middle and some at extreme ends.
What two statistics can summarise the normal distribution?
The mean and the standard deviation.
Extreme outer centiles have been added to UK growth charts - describe these.
2/3 of the standard deviation further out so 0.4 and 99.6 percentiles
What is the advantage of the UK extreme outer centiles?
If children are out with these limits then they are very unusual and worth investigating whereas being within the +/- 2 standard deviations a child may still be normal.
What is the standard deviation score also known as?
The Z score
On UK90 growth charts, what centiles are represented by the lines?
98th, 91st, 75th, 50th, 25th, 9th and 2nd.
What will a child’s standard deviation score be if they are completely normal?
0
How would you explain to a parent that their child is in the 25th percentile for height?
- Out of 100 healthy children, the same age and gender, if you line them all up in height order then their child would have 75 children taller than them and 25 children shorter.
- The child is within normal range but below average height.
The ideal growth chart would be…
- Based on healthy, breast fed infants as the physiological norm
- Based on children who were breastfed for recommended time
- Based on children of mothers in reasonable environmental conditions
- Demonstrate how healthy children should grow.
How did the WHO aim to build the ideal growth chart?
- Six different cohorts throughout the world collected data using the same protocol and stringent inclusion criteria.
- Only healthy children were included in the sample.
- Mother breastfed for at least 4 months and partially for a year.
- Mother did not smoke during pregnancy.
- Mothers had to be reasonably prosperous (definition of prosperity varied according to region).
- Sample of first two years of life was longitudinal.
- Same from age 2-5 was cross sectional.
What did the WHO growth charts prove in terms of height?
That healthy children should grow in the same pattern throughout the world.
Why might weight data vary more than the height data?
Weight is more sensitive to immediate environmental conditions and variations.
