Childhood growth Flashcards
Define growth:
change in body size over time (height, weight, BMI)
How would you plot and label a growth chart?
growth rate/velocity = slope of line
time = x-axis
size = y-axis
Why is growth the unique paediatric indicator of well-being?
it monitors child endocrine, nutritional, emotional and physical health
Who published the first growth curve, and when?
Le Comte de Montbeillard (for his son), in 1777
Why should we assess growth?
- identify abnormal growth
- specify a growth disorder
- proxy for general ill health
What are the growth assessment principles?
- Purpose to distinguish abnormal from normal
- Needs high quality measurement (training, calibration, quality control)
- Correct recording (chart plotting and interpretation)
What is a centile?
percentage point of the frequency distribution
e.g. cut-off that identifies that percentage of children with measurements below it
What must be made sure of centiles and SD scores?
- normally distributed
- each centile corresponds to number of SDs above/below the mean (SD score = z-score)
In a growth distance and velocity chart, what does “current size” indicate?
distance travelled
In a growth distance and velocity chart, what does “centiles crossing” indicate?
velocity of travel
When the growth chart quantifies size/distance, we say it is….
centile
When the growth chart does not quantify growth velocity, we say it is….
centile crossing uncalibrated
What is the nine centile format?
improved cut-offs for screening (2nd and 0.4th centile replace 3rd centile)
- pick up rate of different screening strategies in this
- clear recommendation for referral
Let’s say you’re looking at child growth, the 3rd centile would pick up how much % of children?
3% (1 in 33)
Let’s say you’re looking at child growth, the 2nd centile would pick up how much % of children?
2.3% (1 in 44)
Let’s say you’re looking at child growth, the 0.4th centile would pick up how much % of children?
0.4% (1 in 260)
What is the aim in, lets say, constructing growth charts?
to define weight distribution at each age
What 3 things could be noted from constructing growth charts?
- skewness
- nonlinear age trend
- variability changes with age
Who came up with the LMS method?
Cole, 1998
What is the LMS method?
- splits data into narrow age groups
- summarises skew weight distribution in each group
What are the variables in LMS method?
- Power transform λ
- mean μ
- coefficient of variation σ
Why is it called LMS method?
L = curve for λ M = curve for μ S = curve for σ
What is the formula for the LMS method
Centile(100α) =M x (1+LSzα)^(1/L)
What is the formula for SD score from LMS method?
SD score = (measurement /M)^(L) − 1 DIVIDED BY (LS)
Who came up with Cole-green LMS method?
peter green, 1988
Why was the Cole-green method formulated?
proposed to use maximum penalised likelihood to improve LMS method
- elegantly avoids arbitrary age groupings
- now the STANDARD METHOD
How many countries use LMS method?
40
What did the British 1990 chart include?
- Weight
- Height/length
- BMI
- Head circumference
- waist circumference
What did the Personal Child Health Record (PCHR) include?
- weight
- length/height
- head circumference
what is the diff between growth reference and growth standard?
reference = shows how children DO growth standard = shows how children SHOULD grow, based on healthy reference population
When did WHO publish the current growth standard?
2006
What does the WHO growth standard include?
- sample breast-fed infant and children of non-smoking, non-deprived mothers from six countries (USA, norway, india, ghana, brazil, oman)
- very similar linear growth patterns in all centres
- chart describes optimal not average growth
- suitable for all children
What does the length graph of the WHO standard growth show?
- similar length across sites
- growth potential is independent of ethnicity
What is the comparison of the British 1990 and the WHO standard weight chart for breast-fed infants?
British = 50:50 breast-fed and formula-fed infants
WHO = entirely on breast-fed infants
What explains both relevance and irrelevance of using British 1990 charts?
- for height, it’s accurate for current children
- little sign of secular trend
- for weight, and BMI, it’s out of date though
- and the centiles for weight and BMI no longer feasible on any chart
What does the UK-WHO chart development include?
- WHO charts from age 2 weeks to 4 years
- continues using British 1990 from age 4-20 years and birth and pre-term data
- RCPCH design charts and produce educational materials
- developed by expert group and tested in focus groups of staff and parents
What is obesity again?
form of abnormal growth, malnutrition
- excess body fat
What is used to measure fat?
simple anthropometry
- weight
- weight for height
- BMI
- waist circumference
What is the purpose of BMI chart?
important for both clinical and public health
What are the centiles used in the BMI chart?
- 91st and 98th centile as the clinical cut-off
- 85th and 95th for public health monitoring (but this is not on the chart)
(P.s. IOTF international cut-offs for overweight and obesity included)
What does the waist circumference chart include and exclude?
- BMI ignores body composition (weight shifting between muscle and fat not detected)
- waist circumference useful measure of abdominal fat (subcutaneous and internal)
What initially happened in the child BMI history?
- all the definitions of obesity from published papers had varying specification reference sample and centile cut-off
- cannot compare across studies
- hence NEED UNIFYING INTERNATIONAL REFERENCE
What is the proposal of the International Obesity Task Force (IOTF)?
- use BMI centiles to assess childhood overweight/obesity
- centiles to pass through 25-30kg/m2 at 18yo
- pool centiles from 6 large national surveys (brazil, britain, netherlands, hong kong, singapore, USA)
What was the outcome for IOTF?
- established standard definition for child overweight and obesity
- body mass index cut-off to define thinness
- BMI made cut-offs for thinness, overweight, and obesity
What did the national child measurement programme include?
- BMI of children in reception age 4-5 and year 6 (age 10-11)
- assessed using 91st and 98th british 1990 centiles
- parents told if child overweight/obese
Why should childhood obesity be monitored?
- prevalence high and strong
- BMI and waist charts becoming out of date
- charts need to be frozen so cut-off does not rise which prevalence
- childhood fatness is a poor predictor of adult fatness
- little value in targetting individuals unless severely obese
- high BMI itself insufficient reason for obesity referral
What is the mean age at peak height of the modelling height puberty chart?
12-14 years
Why is the SITAR used to model growth curves?
adjust size, timing, and rate of puberty to superimpose individual curves
- summaries the chaos of pubertal growth in just 3 parameters per child
- efficiently estimates mean growth curve
- useful for life course studies to relate early growth to later adverse outcome
