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Methods Of Nutritional Assessment
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Anthropometric Measurements
WHAT IS ANTHROPOMETRY?
Anthropometry is the measurement of body size, weight, and proportions.
Measures obtained from anthropometry can be sensitive indicators of health,
development, and growth in infants and children.
Anthropometric measures can be used to evaluate nutritional status, whether it be
obesity caused by over nutrition or emaciation resulting from protein-energy
malnutrition.
They are valuable in monitoring the effects of nutritional intervention for disease,
trauma, surgery, or malnutrition. Anthropometry also is considered the method of
choice for estimating body composition in a clinical setting.
MEASURING LENGTH, STATURE, AND HEAD CIRCUMFERENCE
•
Measurements of length, stature (or height), weight, and head
circumference are among the most fundamental and easily obtained
anthropometric measurements. Among infants and children, these
measurements are the most sensitive and commonly used indicators of
health.
• A child’s growth and development can be assessed by comparing height for
age, weight for age, weight for height, and BMI for age with standards
obtained from studies of large numbers of healthy, normal children.
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• The measurement of stature is important for calculating certain indices
such as weight for stature, weight divided by stature, and for estimating
basal energy expenditure.
• In measurements of length and stature, reference will be made to
positioning the head in the Frankfort horizontal plane. As shown below, this
plane is represented by a line between the lowest point on the margin of
the orbit (the bony socket of the eye) and the tragion (the notch above the
tragus, the cartilaginous projection just anterior to the external opening of
the ear). With the head in line with the spine, this plane should be
horizontal.
Length
• Length (also referred to as recumbent (horizontal) length) is obtained with
the subject lying down and generally is reserved for children less than 24
months of age or for children between 24 and 36 months of age who
cannot stand erectly without assistance.
• The growth charts used for persons birth to 36 months of age are based on
recumbent length, whereas the growth charts for those age 2 to 20 years
are based on stature.
• Measurement of recumbent length requires a special measuring device
with a stationary headboard and moveable foot- board that are
perpendicular to the backboard. The device’s measuring scale (in
millimeters or inches) should have its zero end at the edge of the
headboard and allow the child’s length to be read from the footboard.
• Two persons are required to measure recumbent length. as shown below
.With the child in the supine position (lying on his or her back), one person
holds the child’s head against the backboard, with the crown securely
against the headboard and with the Frank- fort plane perpendicular to the
backboard.
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• This person also keeps the long axis of the child’s body aligned with the
center line of the backboard, the child’s shoulders and buttocks securely
touching the backboard, and the shoulders and hips at right angles to the
long axis of the body.
•
The other person keeps the child’s legs straight and against the backboard,
slides the footboard against the bottom of the feet (without shoes or socks)
with the toes pointing upward, and reads the measurement. The footboard
should be pressed firmly enough to compress the soft tissues of the soles
but without diminishing the vertebral column length.
• Length should be recorded to the nearest 0.1 cm or in., using a consistent
unit over
• repeated measurements. Gentle restraint is often required to keep a
squirming infant properly positioned during measuring. When this is not
possible, the best estimate should be recorded with a notation of the
circumstances.
Stature
• Stature, or standing height, can be measured for subjects 2 to 3 years of
age and older who are cooperative and able to stand without assistance.
Stature can be measured in several ways.
• The simplest is to fasten a measuring stick or nonstretchable tape measure
to a flat, vertical surface (for example, a wall) and use a right-angle
headboard for reading the measurement, If a wall is used, it should not
have a thick baseboard, and the subject should not stand on carpet, which
could affect the accuracy of measurements.
• Using the moveable rod on a platform scale is not recommended because it
often lacks rigidity, the headboard is not always correctly aligned, there is
no rigid surface against which to position the body, and the platform height
will vary depending on the subject’s weight. Another approach is to use a
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stadiometer, such as the Harpenden stadiometer or one manufactured by
Seca Corporation or Measurement Concepts.
• When being measured with the stadiometer, the subject should be
barefoot and wear minimal clothing to facilitate correct positioning of the
body. The subject should stand with heels together, arms to the side, legs
straight, shoulders relaxed, and head in the Frankfort horizontal plane
(“look straight ahead”). Heels, buttocks, scapulae (shoulder blades), and
back of the head should, if possible, be against the vertical surface of the
stadiometer.
• Some people may not be able to touch all four points against the
stadiometer because of obesity, protruding buttocks, or curvature of the
spine. Rather than creating an embarrassing situation by trying to force a
subject into
• a physically impossible position, have the subject touch two or three of the
four points to the vertical surface of the stadiometer or estimate height
from knee height.
• Just before the measurement is taken, the subject should inhale deeply,
hold the breath, and maintain an erect posture (“stand up tall”) while the
headboard is lowered on the highest point of the head with enough
pressure to compress the hair).
• The measurement should be read to the nearest 0.1 cm or in. and with the
eye level with the headboard to avoid errors caused by parallax, which is a
difference in the apparent reading of a measurement scale.
Nonambulatory Persons
• In nonambulatory persons (those unable to walk) or those who have such
severe spinal curvature that measurement of height would be inaccurate,
stature can be estimated from knee height.
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Head Circumference
• Head circumference measurement is an important screening procedure to
detect abnormalities of head and brain growth, especially in the first year
of life. Although these conditions may or may not be related to nutritional
factors, discussion of head circumference measurement is included here for
convenience.
• Head circumference increases rapidly during the first 12 months of life but,
by 36 months, growth is much slower,’0 Therefore, it is recommended that
head circumference be measured routinely on infants and young children
up to age 36 months.
• Head circumference is most easily measured when the infant or child is
sitting on the lap of the caregiver, although older children can be measured
when they are standing.
• A flexible. nonstretchable measuring tape is required. Objects such as pins
should he removed from the hair. As shown below, the lower edge of the
tape should be positioned just above the eyebrows, above not over) the
ears, and around the back of the head, so that the maximum circumference
is measured.
• The tape should be in the same plane on both sides of the head and pulled
snug to compress the hair. The measurement is read to the nearest 0.1 cm
or in. and written in the infant’s file. Reliability of the measurement should
be verified with a second reading.
MEASURING WEIGHT
One of the most important measurements in nutritional assessment is
body weight. Weight is an important variable in equations predicting
caloric expenditure and in indices of body composition.”
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• Body weights should be obtained using an electronic scale or a
balance-beam scale
• Compared with balance beam scales, electronic scales tend to be
lighter in weight, somewhat more portable, and faster and easier
to use. They provide easy-to-read digital output in either metric or
English units and, when properly calibrated, are highly accurate
• Errors are commonly made in reading scale, dials, and rulers. The
large. easily read digital output from electronic scales can help
reduce this error.
• Digital scales can record a subject’s weight quickly. This can be an
advantage in weighing infants, who tend to resist lying still for very
long.
• Scales should be placed on a flat, hard surface that will allow them
to sit securely without rocking or tipping. The zero weight on the
scale’s horizontal beam should be checked periodically and after
the scale has been moved.
• On balance beam scales this can be done by sliding the main and
fractional weights to their respective zero positions and adjusting
the zeroing weight until the beam balances at zero. Two or three
times a year the accuracy of the scales should be further assured
by using standard weights or by a professional dealer.
• Because spring-type bathroom scales may not provide the
required accuracy after repeated use, they are not recommended.
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• Balance-beam scales with wheels that are moved from one
location to another are not recommended either because scales
must be recalibrated every time they are moved
• Infants
• Infants should be weighed on a pan-type pediatric electronic or
balance-beam scale that is accurate to within 10 g (0.01 kg) or
0.5 OZ. Any cushion (for example, either a towel or diaper) used in
the pan should be in place when the zero adjustments are made
on the scale or its weight should be subtracted from the infant’s
weight..
• Whatever practice is used, it must be uniformly followed and
noted in the infant’s file. Infants can be weighed nude, or the
weight of the infant’s diaper can be weighed nude, or the weight
of the infant’s diaper can be subtracted from the infant’s weight.
The infant should be set lying down in the middle of the pan.
• The average of two or three weightings is recorded numerically in
the infant’s file to the nearest 10 g (0.01 kg) or .5 oz and then is
plotted on the growth chart in the presence of the subject’s caregiver. If, on comparison with previous data, the current values
appear unusual, the measurements should be repeated.
• Excessive infant movement can make it difficult to obtain an
accurate weight, in which case the weighing can be deferred until
later in the examination. When too active to weigh on a baby
scale, an infant can be weighed on a platform scale while being
held by an adult with the weight derived by difference.
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• Children and Adults
• Children and adults who can stand without assistance are weighed
on a platform electronic or balance-beam scale that is accurate to
100 g (0.1 kg) or .25 lb. The subject should stand still in the middle
of the scale’s platform without touching anything and with the
body weight equally distributed on both feet.
• The weight should be read to the nearest 100 g (0.1 kg) or .25 lb
and recorded. Two measurements taken in immediate succession
should agree to within 100 g (0.1 kg) or .25 lb.’ The weight of
children then can be plotted on their growth charts.
• Ideally, children and adults should be weighed after voiding and
dressed in an examination gown of known weight or in light
underclothing with the scales placed where adequate privacy is
provided. Should the weight of clothing be subtracted from the
subject’s weight? It depends on the purpose for which
measurements are obtained and how accurate they need to be.
• In settings requiring a high degree of accuracy, subjects can be
clothed in an examination gown of known weight for which
consideration can be easily made. In situations having somewhat
less stringent requirements, a reasonable estimate of clothing
weight can be subtracted from a subject’s weight.
Nonambulatory Persons
• Persons who cannot stand unassisted on a scale can be weighed in
a bed scale or chair scale. The subject to be weighed in the bed
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scale is comfortably positioned in the weighing sling, which then is
gently raised until the subject is suspended off the bed. In a chair
scale, the subject sits upright in the center of the chair while
leaning against the backrest
• Using either method, once the subject is still, weight can be read
and recorded to the nearest 100 g (0.1 kg) or .25 lb. Reliability of
the measurement can be verified with a second reading, which
should agree to within 100 g or ¼ lb.’
• SKINFOlD MEASUREMENTS
• The most widely used method of indirectly estimating percent
body fat in clinical settings is to measure skinfolds—the thickness
of a double fold of skin and compressed subcutaneous adipose
tissue .
• Although more accurate methods for assessing percent body fat
exist, SKINFOlD measurement has these advantages: the
equipment needed is inexpensive and requires little space
measurements are easily and quickly obtained; and, when
correctly done, skinfold measurement provides estimates of body
composition that correlate well with those derived from
hydrostatic weighing. the most widely used laboratory method for
determining body composition.
• Measurement Technique
• Proper measurement of skinfolds requires careful attention to site
selection and strict adherence to the following protocol, which is
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standard among researchers who developed the prediction
equations for determining fatness from skinfold measurements.
• 1-Most North American investigators (including those conducting
large national surveys rum which reference data are derived) take
skinfold measurements on the right side of the body. European
investigators typically perform measurements on the left side.
From a practical standpoint, it matters little on which side
measurements are taken.
• 2. As a general rule, those with little experience iii skinfold
measurement should mark the site to be measured once it has
been carefully identified . A flexible nonstretchable tape measure
can be used to locate midpoints on the body.
• 3. The skinfold should be firmly grasped by the thumb and index
finger of the left hand about I cm or 0.5 in. proximal to the skinfold
site and pulled away from the body. This is usually easy with thin
people, but it may be difficult with the obese and may be
somewhat uncomfortable.
• 4. The caliper is held in the right hand perpendicular to the long
axis of the skinfold and with the calipers dial facing up and easily
readable. The caliper tips
• should be placed on the site and should be about 1 cm or .5 in.
distal to the fingers holding the skinfold .
• 5. The caliper should not be placed too deeply into the skinfold or
too close to the tip of the skinfold. The measurer should try to
visualize where a true double fold of skin thickness is and place the
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caliper tips there. It is a good practice to position the caliper arms
one at a time on the skinfold.
• 6. The dial is read approximately 4 seconds after the pressure from
the measurer’s hand has been released on the lever arm of the
caliper. If caliper tips exert force for longer than 4 seconds, the
reading will gradually become smaller as fluids are forced from the
compressed tissues.
• 7. A minimum of two measurements should be taken at each site.
Measurements should be at least 15 seconds apart to allow the
skinfold site to return to normal. If consecutive measurements
vary by more than 1 mm, more should be taken until there is
consistency.
• 8- Measurements should not be taken immediately after exercise
or when the person being measured is overheated because the
shift in body fluid to the skin will inflate normal skinfold size.
• 9-. It takes practice to consistently grasp skinfolds at the same
location every time. Accuracy can be tested by having several
technicians take the same measurements and comparing results. It
may take up to 50 practice sessions to become proficient in
measuring skinfolds.
• Several types of skinfold calipers are available). The Lange skinfold
caliper is most popular among U.S. Several less expensive plastic
calipers are available, such as the Slim Guide and the Fat-Control
Caliper.
• Some of the plastic calipers have been shown to give results
comparable to the more expensive calipers.
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