lab exercise 2 anthropometric assessment -...

1

NUT 112: Lab 1 2012

Student name: Dana Shintani

Lab Exercise 2

Anthropometric Assessment (154 points)

Introduction

Nutritional anthropometry refers to the measurement of body weight and dimensions, and the subsequent

interpretation of the measurements in relation to appropriate reference data. A broad range of anthropometric

techniques used for assessing adults and children will be described in class, lab (this week and next), and the

suggested reading material. Linear growth is measured as supine (recumbent) length in children less than two

years of age and as stature (standing height) in older children and adults. By the end of this exercise, you will:

1. Plot anthropometric data from individual children and interpret their patterns of growth

2. Calculate Z-scores, percent median and percentiles from anthropometric data, both “manually” and

by using a computer program.

3. Observe a demonstration of measurements of weight, length, and head circumference of children,

using standard procedures.

4. Measure the weights and heights of adults and evaluate the within-observer and between-observer

error of the measurement.

1. Use the data in the following table to complete this set of questions. Plot the data on the

accompanying WHO growth chart for both children.

a. Using the WHO Growth Charts, plot the following data on the appropriate chart. Multiple

children can be plotted on the same chart. Be sure to label which plots correspond to which

child. (45 points)

Weight-for-age for Jordan, Hillary & Laura

Length-for-age for Jordan, Hillary & Laura

Weight-for-length for Jordan, Hillary & Laura

2

NUT 112: Lab 1 2012

Student name: Lab TA:

Table 1. Weight and length measurements for three children

Age (mo)

Hillary (female) Jordan (male) Laura (female)

Weight (kg) Length (cm) Weight (kg) Length (cm) Weight (kg) Length (cm)

1 --- --- 4.7 54.9 3.9 55.2

2 5.8 61.0 5.7 58.4 -- --

3 6.9 63.4 6.6 61.1 -- --

4 7.5 66.7 --- --- -- --

5 8.4 67.3 7.9 66.1 -- --

6 8.5 70.5 8.4 67.4 -- --

7 8.8 70.8 8.5 68.9 7.5 63.1

8 9.4 72.1 8.6 69.2 -- --

10 9.6 75.9 8.5 70.7 -- --

12 10.1 80.0 8.8 73.2 11.2 75.9

15 11.1 81.9 --- --- -- --

18 12.3 84.4 9.6 76.0 -- --

19 -- -- -- -- 13.8 80.9

24 -- -- -- -- 17.3 95.3

3

NUT 112: Lab 1 2012


b. Interpret these plots. Indicate whether you think the growth pattern is normal or possibly indicative of

some problem. Provide at least one complete sentence for each plot: (10 points)

Weight-for-age, Hillary:

Hilary’s growth pattern is normal; she remains in between the 85th

and the 97th

percentile

Weight-for-age, Jordan:

Jordan’s growth pattern is normal; he remains in the 50th

percentile

Length-for-age, Hillary:

Hilary’s growth pattern is normal; fluctuates between 85

th and 97

th percentile but normalizes as she ages

Weight-for-length, Jordan:

Jordan’s growth pattern is normal; he remains in the 50th

percentile

Weight-for-length, Laura

Laura’s growth pattern is possibly indicative of some problem she goes from the 3rd

to 85th

to 97th

percentile and may be at risk for overweight obesity issues

c. Using the WHO Growth Standards tables, calculate Z-scores for weight-for-age, length-for-age, and

weight-for-length for Jordan at 6 and 18 months age. The simplified formula to calculate z-scores is:

Use the attached tables to determine the appropriate median value and standard deviation to use.

Record the results in Table 3. WHO has used a more sophisticated formula to estimate their z-score

values based on a growth curve smoothing method. Use the WHO Anthro software to calculate z-

scores and compare them to your hand-calculated values. Use the WHO cut-offs below to interpret

your results in Table 3.

Table 2: Interpretation of anthropometric indicators in children

Indicator interpretation

Z-score cut-points Height-for-age Weight for age Weight-for-height BMI-for-age

<-3 Severely stunted Severely underweight Severely wasted N/A

< -2 SD and > -3 SD Moderately stunted Moderately underweight Moderately wasted N/A

>-2 SD and <+2 SD

Normal height

Normal weight Normal weight-

for-height

Normal BMI-

for-age

> + 2 SD N/A Overweight N/A Overweight

4

NUT 112: Lab 1 2012


Table 3 - Interpretation of anthropometric data – Jordan (male) (32 points)

Age = 6 months Age = 18 months Copy values from Table 5

Weight =8.4 kg

Length =67.4

cm

Copy values from Table 5

Weight =9.6 kg

Length =76.0 cm Calculation Answer Calculation Answer

Weight-for-age z-score: (8.4/7.9540)^0.1257-1/(0.1257*0.10958)

0.52

Weight-for-age z-score: (9.6/10.9385)^0.0211-

1/(0.0211*0.11119) -1.17

Interpretation: Normal


Weight-for-age z-score

(from WHO Anthro)

0.28 Weight-for-age z-score

(from WHO Anthro)

-1.36

Length-for-age z-score (67.4/67.6236)^1-

1/(1*0.03165) -0.10

Length-for-age z-score (76/82.2587)^1-1/(1*0.03279)

-2.32


Interpretation: Moderately stunted

Length-for-age z-score

(from WHO Anthro)

-0.52 Length-for-age z-score

(from WHO Anthro)

-2.68

Weight-for-Length z-

score

(8.4/7.7370)^-0.3521-1/(-0.3521*0.08212

0.99 Weight-for-Length z-

score

(9.6/9.7033)^-0.3521-1/(-0.3521*0.08307)

-0.13



Weight-for-Length z- score (from WHO

Anthro)

0.85 Weight-for-Length z- score (from WHO

Anthro)

-0.13

5

NUT 112: Lab 1 2012


d. Using the growth charts that you plotted, indicate the percentile for weight-for-age

for Jordan at 6 and 18 months. Record the results in Table 5. Note: if the

measurement falls between two of the percentiles provided on the charts, indicate the

percentile range. Use the following classification scheme to interpret these results:

Table 4: Interpretation of child growth percentiles

Percentile

Interpretation

< 3% Malnutrition (underweight, stunted, wasted)

> 97% Overweight (weight-for-height z-score) Above normal limits (weight, height)

Table 5: Interpretation of Jordan’s weight for age percentiles (10 points)

Age = 6 months Age = 18 months

Weight-for-age percentile: 50th to 85th

Weight-for-age percentile: 3rd to 15th



Weight-for-age percentile

(from WHO Anthro)

61st Weight-for-age percentile

(from WHO Anthro)

8.6th

e. Based on what you’ve learned in lecture and lab, list at least 3 differences between

the WHO growth standards and the NCHS/CDC growth references. (3 points)

CDC - Data for well-defined population grouped together - What is - Little data on very young infants WHO - Data on a selected population - What should be - International

f. Shekhar is a 10 month old infant living in India. He has a length-for-age Z-

score of -0.5 and a weight-for-length Z-score of -2.3. (4 points)

Is he most likely acutely or chronically malnourished? Explain your answer.

He is most likely acutely malnourished. His length for age is normal; however, his weight for length tells us he is moderately wasted

What is a possible cause of his condition? Not eating sufficiently to accommodate his growth in height

NUT 112: Lab 1 2012


g. Bibata is 22 months old and lives in Burkina Faso, West Africa. She has a length-for-

age Z-score of -2.5 and a weight-for-length Z-score of -0.8. (4 points)

Is she most likely acutely or chronically malnourished? Explain your answer.

She is most likely acutely malnourished. Her length for age Z score is -2.5 which means she is moderately stunted, however, her weight for length is normal

What are two possible causes of her condition?

Not eating the proper nutrients and not eating sufficiently

h. Rajesh is an 18 month old boy and lives in rural Nepal. His weight-for-length z-score over the

past 4 months is shown here: (4 points)

Age (mo) Weight-for-length z-score

15 -0.8

16 -0.9

17 -1.9

18 -1.3

Is Rajesh malnourished?

No

Is Rajesh’s growth trajectory as expected? Explain your answer.

No, his growth trajectory is not as expected because of the drop in Z score at 18 months

Do you have any concerns about his growth? Would you recommend continued

growth monitoring for Rajesh?

His Z score decreases at 18 mo which is concerning. It would be recommended to continue growth monitoring

i. A question nutritionists are commonly asked is: “We see that adults are different heights in

different countries. How can we use the same growth standards for children across countries?

Don’t genetic differences explain these differences in height?” What is the answer to this

question? (2 points)

Can use the same growth standards for children across countries if measurements are made for both individuals and populations

6

NUT 112: Lab 1 2012


7

2. Break into small groups and to measure weight and height. Practice measuring values of at

least 3 other people. RECORD AND SAVE THE MEASUREMENTS of your own weight

and height for future labs in which you will use this information (Record this on another

sheet of paper in addition to this lab report). (9 points)

Table 6: Height measurements of your small group members

Student 1

Student 2

Student 3

Height (cm):

measurement 1

167.5cm 159.5 cm 158.7cm

Height (cm):

measurement 2

167.3cm 159.7cm 158.6cm

Mean 167.4cm 159.6cm 158.7cm

3. Standardization exercise: You are the head dietician at a large hospital and have 6 new interns.

You have trained them in how to measure the height of patients. Now, you are testing them to see how

accurate and precise they actually are. Four nurses act as the subjects being measured by your interns.

All interns measured the height of each of the subjects one time. Subsequently, the interns then

measured each of the subjects a second time, without access to the first set of results. You also

measured each of the subjects twice. Because you are an experienced anthropometrist, you will act as

the “gold standard” to which the accuracy and precision of your interns is compared. See Table 1 for

the raw data that you and your interns recorded.

You are interested in determining how valid, accurate and precise your interns are. Precision is related

to how similar each intern’s measurements are to each other. Highly precise interns will have very

little variability between their two measurements on each subject. Accuracy is related to how close

each intern’s measurements are to the ‘gold standard’ trainer’s measurements. Highly accurate interns

will have measurements that have very little variability on average from the trainer’s measurements.

Validity is related to accuracy, precision and as well as bias. Interns that measure consistently

differently than the trainer—nearly always higher or nearly always lower—display bias in their

measurements.

NUT 112: Lab 1 2012


Table 7: Height measurements for four subjects by group of new interns

8

Intern

Subject

1

Measurement

2

Measurement

3

Measurement

4

Measurement

1 2 1 2 1 2 1 2

A. Sam

180.9

181.1

156.4

155.9

165.9

165.9

171.6

171.8

B. Lucy

180.9

181.3

156.1

156.1

166.0

165.9

172.1

171.8

C. Britney

181.6

181.1

156.0

155.6

166.1

165.7

171.8

171.7

D. Ella

181.0

180.9

155.3

156.0

166.2

165.7

171.7

171.6

E. William

180.4

180.5

156.8

155.8

165.7

165.6

171.5

171.5

F. Catherine

181.2

180.7

156.3

156.2

166.1

165.6

171.5

171.7

Supervisor (Head dietician)

181.5

181.2

156.4

156.1

166.0

166.0

171.8

171.6

NUT 112: Lab 1 2012


9

a. Calculate the measurement error indicators for Intern 1 (Sam) using Table 8 and the

instructions below.

Step 1. Calculate the difference (d) between Measurement 1 and 2 for Sam’s measurements of

each subject, including the sign (- or +), and record this information in Table 2. Note the sign

in the column labeled “sign 1”.

Step 2: Square the difference for each subject calculated in step 1 and record in the column

labeled “d2"

. Calculate the sum of all the squared differences at the bottom of the column (This

is Σd2).

Step 3: At the bottom of the column labeled “sign”, enter the sum of the most frequently

occurring sign as a fraction of the total number of non-zero signs (e.g., if 3 out of 4 signs are

positive, then enter “3/4 +”; if 1 sign is positive, one sign is zero, and 2 signs are negative, then

enter “2/3 -”).

Step 4: In column O (for Observer), enter the sum of Sam’s measurements 1 and 2 for each

subject.

Step 5: In column S (for Supervisor), enter the sum of your measurements 1 and 2 for each

subject.

Step 6: In column D, enter the difference (O - S ) between the sum of Sam’s measurements and

the sum of your measurements for each subject. Note the sign in the column labeled “sign 2”.

Step 7: Square the difference (O - S) for each subject and record these differences in the

column labeled “D2 ”. Sum the squares at the bottom of the column (this is ΣD

2).

Step 8: As in step 3, sum up the signs in column “sign 2” and enter the fraction at the bottom of

the column.

Step 9: Enter Σd2, signs 1, ΣD

2, and signs 2 on the summary sheet (Table 9). Note: the Σd

2,

signs 1, ΣD2, and signs 2 for the other interns have been calculated for you, and are already

recorded on Table 4.

NUT 112: Lab 1 2012


10

Table 8: Measurement error calculations for Sam (10 points)

Within-observer error

Between-observer error

Subject

Measure 1

Measure 2

d (1-

2) d2 (1-

2)2

Sign 1

(+ or -)

Observer

Supervisor

D

(O-S) D2 (O-

D)2

Sign 2

( + or - )

1

180.9

181.1 0.20 0.04 - 362.0 362.7 0.70 0.49 -

2 156.4 155.9 0.50 0.25 + 312.3 312.5 0.20 0.04 -

3 165.9 165.9 0 0 n/a 331.8 332.0 0.20 0.04 -

4 171.6 171.8 0.20 0.04 - 343.4 343.4 0 0 n/a

Sum 0.33 2/3- -0.57 3/3-

NUT 112: Lab 1 2012


11

b. In Table 9, evaluate each intern’s performance, answering the following 4 criteria for each

intern, and record your evaluations in Table 4 in the "Comments/Evaluation" column. Use the

following criteria to help you complete the table and answer the subsequent questions:

Was the intern precise?

o Σd2 is inversely related to precision.

o Using the assumption that the supervisor’s precision is acceptable, a trainee's Σd2

should be no more than two times the supervisor's Σd

2.

Was the intern accurate?

o ΣD2

is inversely related to accuracy. o Ideally, this value should be equal to zero. o In practice, accuracy is considered acceptable if the value for ΣD

2 is no more than three times

the supervisor's Σd2

Was the intern’s ΣD

2 larger than his/her Σd

2 or does the data need to be reexamined and

recalculated? o An observer's ΣD

2 is generally larger than his or her Σd

2. If this is not the case, the data should

be reexamined and recalculated.

Was there systematic bias between the intern’s 2 measurements or b/t the intern and the head

dietitian?

o There should be about as many "+" signs as there are "-" signs.

o If they are not approximately the same under “signs 1", there is probably some consistent difference b/t measurements 1 and 2 for the intern.

o If they are not similar under “signs 2", there is probably a systematic bias between the

intern and the head dietician.

o In either case, the observer should be re-trained

NUT 112: Lab 1 2012


12

Table 9: Summary sheet (14 points)

Within-observer

error

Between-observer

error

Comments/ Evaluation

Measurer

d

2 Sign 1 D2 Sign 2

Precise?

(yes/no)

Accurate?

(yes/no)

Is there systematic bias? Describe.

Head Dietitian 0.22 3/3 + NA NA n/a n/a n/a

Sam 0.33 2/3- 1.29 3/3- yes no yes

Lucy 0.26 2/3 + 0.6 4/4 - yes yes no

Britney 0.58 4/4 + 0.86 2/3 - no no yes

Ella 0.76 3/4 + 2.1 4/4 - no no yes

William 1.02 2/3 + 3.9 4/4 - no no yes

Catherine 0.55 3/4 + 0.77 3/3 - no no yes

14

Appendix: Instructions for measurements

Stature

Standing height is measured for all individuals >2 years old. Measured using a stadiometer.

1. Subject should remove shoes (and thick socks)

2. Subject should stand with the heels together and feet flat on the ground, knees close together, arms at

sides. Shoulder blades, buttocks, and heels should be positioned against the wall or stadiometer.

3. Eyes should be straight ahead with head positioned in the Frankfurt plane (Figure 1)-- an imaginary

line from the lower orbit of the eyes to the external auditory canal -- should be parallel to the floor

Figure 1: Frankfurt Plane

4. Just before the measurement is taken, ask the subject to inhale deeply, hold their breath, and maintain

an erect posture.

5. Lower the movable head board until it gently touches the crown, or apex, of the head.

6. The reading should be recorded with the examiner’s eyes level with the ruler to avoid errors of

parallax. (See Figure 2)

15

Length

Figure 2: Position for measurement of standing height

Length is measured in children <2 years old or in older children or adults who are unable to stand without

assistance. Two individuals are required to position the child correctly. Measured using a stadiometer.

1. Shoes, socks, and any bulky clothing should be removed from the child.

2. Placed the child on his or her back (supine position) with the length of the body parallel to the long axis

of the measuring board and the eyes facing upward. (Figure 3)

3. The crown of the head should be placed against the fixed headboard and held gently in place by one of

the anthropometrists. The head is positioned so that it is perpendicular to the board (vertical Frankfurt

plane).

4. The second anthropometrist should position the child’s feet, gently pressing the knees straight and flat

against the board and then slide the movable footplate to rest firmly against the child’s heels with the feet flat

against the footplate.

5. The reading should then be recorded.

16

Figure 3: Position for measurement of recumbent length in infants and children < 2 years old.

Weight:

Adults & older children

Weight measurements for adults and older children can be measured using an electronic, digital scale or manual

beam-balance scale. Scales must be periodically checked for accuracy by weighing standard, known weights to

ensure that they are consistently calibrated.

1. Place scale on a flat, hard surface.

2. Subject should be wearing light clothing and should remove their shoes.

3. Ask the subject to step onto the scale and stand without moving. Movement artifacts can alter the

accuracy of the reading. You may need to do the reading quickly for young children.

4. For a beam-balance scale, slide the weights to the appropriate positions and weight until the arm has

balanced.

5. Record the weight.

Infants and young children:

Infants and young children can be weighed several different ways, using a spring-balance, a beam-balance, or a

digital infant tray scale, or by asking an adult to hold the child on standing scale and then subtracting the weight

of the adult. This can be done with modern electronic scales with a tare function.

1. Place the scale on a flat, hard surface.

2. The child should be very lightly clothed with shoes removed

3. For infant tray-scales (beam balance and electronic), place the child in the center of the tray and wait

until the child is lying or sitting quietly to record the measurement.

4. For standing scales, ask the child’s caregiver to stand on the scale alone and record their weight. If

17

possible, tare the scale to zero. Then hand the child to the caregiver and record the weight of the

child+adult. Wait until the child is still before recording the measurement.

Head Circumference:

Measures of head circumference are obtained in children up to 36 months of age to screen for abnormal

brain development and structural abnormalities. Head circumference is measured with a thin, non-stretchable

measuring tape or special “insertion tape”. The child can be measured in either a sitting or supine position.

1. Remove any hats or hair ornaments that may interfere with the placement of the tape. 2. The child’s head should be positioned in the Frankfurt plane.

3. The tape should be placed over the most prominent part of the frontal bulge, above the superior orbital

ridge, and is then wrapped around the occipital prominence at the site that provides the largest

circumference.

4. The tape should be pulled tightly to flatten the hair before the reading is taken.

Figure 4: Measurement of head circumference

18

Instructions for using the WHO Anthro Software Download the free software from http://www.who.int/childgrowth/software/en/ Click on the “WHO Anthro

for PC” link and follow the installation instructions to save the program to your computer.

1. Open the “WHO Anthro” program from the ‘Start/Programs’ meu.

2. Click on the “Anthropometric calculator” button

3. Input data for the child. If you only know the child’s age, but not

birthday, make up dates to get an appropriate calculated age.

4. Be sure to select the correct

method of recording length

(recumbent, for children <2

y) or height (standing, for

children >2 y)

5. Be sure to select whether

the child has oedema (No,

in all of our lab exercises)

6. Record the displayed z-scores. NOTE: These will be different than your hand-calculated values.

http://www.who.int/childgrowth/software/en/

lab exercise 2 anthropometric assessment -...

Documents