Nutritional anthropometry. Identification of groups at risk of morbidity and mortalitySurveillance Tool for individual monitoring and intervention. Anthropometric Tools. Weight scale (calibration, accuracy, fluctuations, ability to read)Heightboard for recumbent (0.5 cm longer)various mean
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1. Nutritional Assessment & Monitoring Global Health 531
Research Methods for Developing Countries
Stephen Gloyd, MD, MPH
Professor, Dept. of Global Health
2. Nutritional anthropometry Identification of groups at risk of morbidity and mortality
Tool for individual monitoring and intervention
3. Anthropometric Tools Weight
scale (calibration, accuracy, fluctuations, ability to read)
board for recumbent (0.5 cm longer)
various means for upright (standing)
Arm Circumference: tape
7. Most Common Indicators Weight for Height (W/H) - "wasting"
Height for Age (H/A) - "stunting"
Weight for Age (W/A) – “growth faltering”
Median Upper Arm Circumference (MUAC)
8. Other Indicators % Growth faltering
% Discharges/admissions to hospitals with malnutrition
BMI (Body Mass Index)
9. Body Mass Index (BMI) compares a person's weight and height
usually used for adults (kids have BMI for age)
does not actually measure the percentage of body fat, it is a useful tool to estimate a healthy body weight
BMI = weight (kg)/height2 (m)
Normal 18.5 – 25.0 (over 30-obese, under 17-anorexia)
10. Measuring Other Nutritional States Iron Deficiency
Vitamin A deficiency
11. Weight for Height (W/H) "wasting" Advantages:
age not required
good for nutritional emergencies
difficult to measure height
12. Height for Age (H/A) "stunting" Advantages:
frequently associated with poor overall SES conditions
picks up lots of kids in developing countries
difficult to measure height
13. Weight for Age (W/A) “growth faltering” Note: Composite index of W/H and H/A
good for following individual kids in sequential measurements
fails to distinguish tall, thin kids from short, adequate muscle mass kids
poor predictor of "wasting" in three US populations
14. Scales of Choice % median
16. % of Median more common in older literature.
useful if the distribution around the median is unknown or reference population has not been normalized.
simple to calculate (vs z-score or percentile)
varies across age and height groups - because it is independent of distribution of reference population.
each cut-off value differs according to index
18. Percentiles Usually have uniform distribution.
Easy to interpret.
Not usually distributed normally.
Less useful in describing extremes of distribution.
Should not be described in terms of means and SDs.
19. Z-scores Most frequently used today
Multiple computer programs with anthropometric z-score distribution
H/A, W/A, W/H have normal distribution at each age (in months)
Statistical methods are easier to perform with this method.
21. Means Reflects changes and relationships among whole population
Generally varies with z-score
More statistical power than other scales
23. Scale of Choice - more scale of measurement usually does not affect prevalence of low anthropometry - if age specific or age-standardized
Age distribution will affect prevalence with different indices (coefficient of variation changes through childhood, especially in the first two years)
z-scores and % of median differ according to weight and height
25. Reference Populations WHO/CDC reference curves are derived from FELS and NCHS
Most software (Anthro, Epi-Info, Epi-Nut) use FELS up to 24 months
FELS: white, middle class, longitudinal follow-up
NCHS: representative of all USA children, cross-sectional
Linear growth measured differently in the two groups
FELS - recumbent lengths
NCHS - standing heights
Thus, FELS kids are taller and thinner than NCHS kids
Disjunction where curves meet
26. Reference Populations (2) Most studies will show improvement in anthropometric indicators at age 2
this is due (to a large extent) to the disjunction of the curves from FELS and NCHS
Also, age distribution of population is important in comparing prevalences
31. Median Upper Arm Circumference (MUAC) Advantages
easy to perform
does not require age (relatively age independent?) (graph)
"best" predictor of mortality in children (graph)
multiple cut-off values
Overall -- poor correlation with stunting (figure)
38% measured the same children
33. Patterns of Anthropometric Findings High wasting (>10%) and high stunting (>20%)
High stunting, but low wasting
multiple SES-based causation, including LBW
(specific causes may differ from region to region)
poor correlation between wasting and stunting on individual and ecologic basis, especially in Africa and LA; more correlation in Asia
High prevalence of underweight can be due to either wasting or stunting pattern
34. Patterns of Anthropometric Findings (2) (table of country comparisons)
Proposed epidemiologic criteria for assessing severity of undernutrition (table)
W/A and W/H are very dependent on height (table)
W/A is more useful for following child over time (growth chart)
Underweight -- more correlated with wasting than stunting (Haiti, Palestinian refugees)
little correlation between stunting and wasting
45. Interventions Can see changes with wasting at all ages
Not as useful for stunting over 2 years of age
Overall usefulness: (table)
47. Issues in Choice Availability of accurate equipment
Training of measurers
Time available for measurement
Ability to interpret findings
Costs of not identifying malnourished children
Likelihood of identifying children at risk of dying
51. Labels “Mild", “Moderate", & “Severe" may be misleading Not all children below cut-off are malnourished.
Not all children above cut-off are ok.
Cut-offs indicate which kids are more likely to be malnourished.
*Always best to give age group when discussing anthropometry results
- especially under/over 24 months -- or >85 cm, or <85 cm for weight for height
52. Example of System for Following Children W/A for periodic measurements (if age is known)
If rapid faltering, due to inadequate weight gain (wasting)
If slower, get H/A and W/H to determine cause
56. Individual Growth Monitoring Longitudinal measurements are critical
Decline over time in anthropometric indicators is much more important than single low measurement.
There is no generally accepted definition of "growth faltering".
Single measurements can be useful to classify children (e.g., feeding programs).
Some studies show threshold risk effect.