NUTRITION CORE: Nutrition Assessment Unit
The Nutrition Assessment Unit is a state-of-the-art facility for the assessment of growth and body dimensions,
body composition (the amount of muscle, fat and bone in the body), energy expenditure, bone density, and
muscle strength. The Core provides consultation and technical expertise for these assessments. The Unit has
two locations and four experienced research technicians for performing nutrition assessments. Babette Zemel,
PhD serves as the Core Director.
ANTHROPOMETRIC ASSESSMENT OF GROWTH AND BODY COMPOSITION
The Nutrition Core Laboratory has the capability of performing a wide array of anthropometric measurements
of infants, children and adults to assess growth, body dimensions and body composition. The equipment
available for anthropometric examinations includes: infant (0.01kg), adult (0.1kg) and wheel chair (0.1kg)
accessible Scaletronix digital scales (Scaletronix, White Plains, NY), Harpenden neonatometers and
infantometers for measurement of length and stadiometers for measurement of stature (Harpenden, Crymych,
UK), retractable tape measures (0.1 cm) for measuring circumferences (head, arm, waist, hip, etc.), skinfold
thickness calipers (0.1mm) (Holtain, Crymych, UK) to assess regional subcutaneous fat stores (e.g., biceps,
triceps, subscapular, suprailiac skinfold thicknesses) and/or body composition (fat mass, fat-free mass, and
percent body fat), and a variety of sliding calipers (0.1 cm) and anthropometers (0.1 cm) to measure body
breadths (e.g., elbow breadth, biacromial diameters) and limb lengths (forearm, lower leg) as indicators of body
proportions or alternative measures of linear growth. Abdometers are available for the measurement of sagittal
abdominal diameter, an anthropometric correlate of intraabdominal fat. In addition, the Nutrition Core
Laboratory has several high precision knee height measuring devices which measures the length of the lower
leg from the heel to the superior surface of the knee for the assessment of short-term growth of the lower leg
(0.01 mm)1.
Assessment of sexual maturation is often included in the anthropometric examination. The Nutrition Core
Laboratory provides a self-assessment questionnaire originally designed by Morris and Udry2 that uses
pictograms and descriptions for breast stage in girls, genital stage in boys, and pubic hair development in both
boys and girls based on the sexual maturity stages defined by Tanner3. The questionnaire is explained to the
study participant (with or without a parent present) in advance, and then they are left to complete the
questionnaire in private. The anthropometric exam room is equipped with a full length mirror to aid in the self
assessment process.
The Nutrition Core Laboratory has four highly trained research anthropometrists. Most measurements are
obtained in triplicate to provide a robust measurement, and to monitor precision and intra-observer reliability.
Anthropometric examination protocols are modified to meet the needs of the investigator and the study
population. Dr. Zemel, Director of the Nutrition Core Laboratory, is available for consultation on the selection of
measures, study design, computations of derived measures, and selection of reference data for interpretation.
Costs associated with the anthropometric exam are derived from the estimated staff time for
scheduling the study participant, performing the examination, and processing results, and office
supplies for the collection and processing of the data. There are no equipment related charges for this
procedure.
BODY COMPOSITION:
The Nutrition Core Laboratory has several methods available for body composition assessment.
Pea Pod Air Displacement Plethysmography (Life Measurement Instruments, Concord, CA) is a safe,
noninvasive, reliable, accurate and brief (approximately 7 minutes) test for infants to estimate fat mass, fat-free
mass and percent body fat using menu driven software4. Body mass, volume, density and surface area are
also determined. Sedation is not required and it can accommodate infants weighing between 1 kg and 8 kg
(17.6 lbs). The unit is semi-portable and can be taken to the bedside. The Infant TOBEC device also assesses
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fat mass, fat-free mass and percent body fat by total body electrical conductivity5. This safe, non-invasive,
rapid device is able to assess infants from birth up to two years of age.
For children and adults, a variety of body composition options are available. The Nutrition Core Laboratory has
two multifrequency bioelectrical impedance analyzers (RJL Systems, Clinton Township, MI) to obtain noninvasive, rapid measurements of total body water, fat-free mass, fat mass, percent body fat of the total body
and body segments based on resistance and reactance measurements. The device is small and portable. The
Bod Pod Body composition analyzer (Life Measurement Instruments, Concord, CA) obtains body
composition measurements based on air displacement (similar to the Pea Pod) in children and adults6. The
technique is rapid and non-invasive. The device includes an option to either directly measure thoracic gas
volume (TGV), or use prediction equations. The output includes measurements of fat free mass, fat mass,
percent body mass, and body mass and density. A distinct advantage of the BOD POD is its ability to
accommodate a wide variety of human shapes and sizes such as tall (up to 7 ft) and obese (up to 550 pounds)
individuals. In order to obtain accurate results, subjects must be tested in form-fitting clothing such as a Lycra®
or Spandex® swimsuit or single-layer compression shorts. A swim cap must also be worn to compress any air
pockets within the hair. Costs associated with Bod Pod tests include the shorts or swimsuit if the study or study
participant does not provide their own.
Other body composition techniques include whole body DXA scans and anthropometric assessment. These
are described in other sections.
Four highly skilled research technicians are available for performing these body composition tests. Costs for
body composition assessment are based predominantly on the hourly rate for the technicians
performing the tests. Additional charges for supplies such as electrodes, breathing tubes, swimsuits,
printer cartridges, and replacement cost of each device are incorporated into the cost for each test.
BONE HEALTH ASSESSMENT:
The Nutrition Core Laboratory offers three techniques for bone health assessment. Each technique is available
at both Nutrition Core Laboratory locations.
Quantitative Ultrasound (QUS): the McCue CUBA Contact Ultrasound Bone Analyzer device (Wilburn
Medical USA, Kernersville, NC 27284) performs a quantitative ultrasound measurement of the calcaneus. It
measures the Speed of Sound (SOS, m/s) and broadband ultrasonic attenuation (BUA, dB/MHz) of an
ultrasound beam passed through the heel. The scatter of the ultrasound wave by the bone is indexed by the
bone ultrasound attenuation (BUA) and speed of sound (SOS). These measures relate to bone density and
architecture. The calcaneus site is ideal because it has a high proportion of trabecular bone, and it is a weightbearing, easily accessible, peripheral site. The McCue CUBA is unique for use in children because it has both
pediatric and adult size transducers. The test is rapid, safe and does not involve any radiation. Daily QC
checks are performed with a phantom supplied by the manufacturer. Measurements are obtained in triplicate
by trained technicians. Costs for QUS measurements are based on the hourly rate for the technicians
performing the tests, related supplies (e.g., ultrasound gel, printer cartridges), and the replacement
cost of the device.
Peripheral Quantitative Computerized Tomography (pQCT) is a research tool that assesses trabecular and
cortical bone dimensions and strength in the peripheral skeleton (Stratec XCT 2000, Orthometrix, White Plains,
NY). The Stratec XCR 2000 is a rotate-translate QCT device with 12 detectors with a minimum voxel size of
0.4mm.
Measurements are typically taken of the distal tibia at the 3%, 38% and 66% from the distal reference line at
the tibia growth plate. Comparable measurements can be obtained in the distal radius. The 3% site is primarily
trabecular and gives a volumetric measure of trabecular BMD. Total volumetric BMD at the 3% site provides an
integrated measure of cortical and trabecular density at a distal site. The 38% site provides measures of
cortical volumetric BMD, as well as structural parameters such as periosteal and endosteal circumference and
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cross-sectional moment of inertia (index of bone strength). The 66% site of the tibia is the location of maximal
muscle circumference and will be used to evaluate the effect of local body composition (i.e., muscle crosssectional area) on bone. Alternate measurement sites at fixed or relative distances from the reference
landmark can be obtained at the request of the investigator. Electronic data sets containing study results can
be provided to the investigator.
The effective radiation dose for the p-QCT measurements is very low
. Phantoms are scanned
daily to monitor quality control of the device. The CTRC Nutrition Core Director, Dr. Babette Zemel, reviews all
scans for quality assurance. The coefficient of variation for QCT measurements in children range between 0.5
to 2.8%7-9. The procedure takes approximately 15 minutes to complete depending on the number of sites
scanned. Local reference data is available on approximately 500 to 700 healthy control children.
The CTRC Nutrition Core is equipped with two research dedicated pQCT devices, one in the satellite CTRC
facility at 3550 Market Street, and the other in the main facility at the Childrens Hospital of Philadelphia. The
CTRC Nutrition Core is staffed by four research technicians who are expertly trained in acquiring pQCT scan
images in children and adults. Electronic data sets of scan results with quality assurance ratings and derived
measures of cortical and trabecular bone density, geometry and strength are provided to investigators.
Charges associated with the pQCT scans represent the direct costs associated with equipment
maintenance and operation (service contracts, supplies, quality control and quality assurance
procedures), replacement cost, and research technician time (research participant preparation,
scanning, image processing and storage, delivery of results to the investigator).
Dual Energy X-ray Absorptiometry (DXA) is the technique most commonly used in the clinical diagnosis of
osteoporosis in adults and low bone mass in children. Bone mineralization of the anterior-posterior spine,
lateral spine, proximal femur, left forearm, and whole body can be assessed by DXA using a Hologic Discovery
bone densitometer (Hologic, Bedford, MA) operating in software version 13.3. Each scan generates a measure
of bone area, BMC and areal-BMD. DXA is also used for body composition assessment. The whole body scan
also provides regional and total body estimates of fat mass, fat-free mass, lean body mass and percent body
fat. All scans are obtained following standardized procedures as recommended by the manufacturer. It takes
approximately 20 minutes to complete all DXA measurements. Instant Vertebral Assessment (IVA) for
determination of spine deformities is also available.
The technique uses very low-dose x-ray exposures
and measurements are rapid, making
this the preferred technique for measurement of bone mineralization in children. Quality control scans are
performed daily using a simulated L1-L4 lumbar spine made of hydroxyapatite encased in epoxy resin and
thrice weekly using a whole body phantom. The in vitro coefficient of variation is < 1% and the in vivo
coefficient in children is < 2%. All scans are reviewed by the CTRC Nutrition Core Director, Dr. Babette Zemel,
or the program manager, Donna Paulhamus, MS, RD, for quality assurance. Electronic data sets containing
study results can be provided to the investigator.
The CTRC Nutrition Core is equipped with two DXA devices, one in the satellite CTRC facility at 3550 Market
Street, and the other in the main facility at the Childrens Hospital of Philadelphia. The CTRC Nutrition Core is
staffed by four research technicians who are expertly trained in acquiring DXA scan images in children and
adults. Electronic data sets with scan results for bone area, content and density, and body composition from
whole body scans are provided to investigators. Charges associated with the DXA scans represent the direct
costs associated with equipment maintenance and operation (service contracts, supplies, quality control and
quality assurance procedures), replacement cost, and research technician time (research participant
preparation, scanning, image processing and storage, delivery of results to the investigator).
MEASURES OF MUSCLE STRENGTH
The Biodex Dynamometer: (Biodex Corp., Shirley, NY) measures muscular strength across joints. The
procedure requires a standardized period of warm-up consisting of 5 minutes of treadmill walking. The subject
then performs an isometric strength test. Typically, plantar flexion and dorsiflexion of the foot are measured
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although other sites are possible. For the ankle, a maximal pain free range of motion (ROM) is established with
the left knee in a neutral position. The subject is then assessed in 1 to 4 positions depending on the total
available ROM: (1) 10 degrees of dorsiflexion, (2) neutral, (3) 10 degrees plantar flexion, and (4) 20 degrees
plantar flexion. Three repetitions of isometric plantar flexion and dorsiflexion are performed at each position. A
five second rest is given between repetitions and a 20 second rest between sets. At each position peak torque
performance is recorded and saved. Trained technicians perform the test. Costs associated with this test
are related to the technician time for the entire procedure (including the treadmill warm-up period) and
the replacement cost of the device.
Hand-Grip Dynamometry: The hand-grip strength dynamometer (Takei Scientific Instruments Co., Ltd.,
Japan) is a hand held device capable of measuring instantaneous hand strength as a function of time for
periods of up to 300 seconds. The subject stands upright with arms extended and is instructed to grip the
dynamometer and exert full force. Three trials are performed using each hand. The dynamometer digitally
displays the force production (kgf) by the subject. The cost of this procedure is based on the technician
time for obtaining and recording the measurements,
Force Plate Jump Mechanography: The Kistler Multicomponent Force Plate (Kistler Instruments AG,
Winterthur, Switzerland) measures jump power, force and height, primarily to determine the functional strength
and muscle loading of the lower limbs, but other applications are possible. Following a warm-up period
consisting of 5 minutes of treadmill walking, the study participant performs the force plate test using a
computer driven standardized jump protocol such as for a squat jump or counter-movement jump. The subject
first completes three practice jumps followed by three test jumps. An electronic database for each test is
generated and provided to the investigator. Costs associated with this test are related to the technician
time for the entire procedure (including the treadmill warm-up period) and the replacement cost of the
device.
INDIRECT CALORIMETRY:
Resting Energy Expenditure (REE) is assessed by open circuit indirect calorimetry using a computerized
metabolic cart (SensorMedics SPECTRA or ENCORE, Yorba Linda, CA). Ideally, tests for children and adults
are performed in the early morning (preferably after an overnight stay in the inpatient CTRC unit) in an awake,
fasted state, with minimal physical activity prior to the test. A standardized evening meal is recommended. A
60-minute REE test is performed between 7:00 and 10:00 AM with the subject resting quietly under a clear,
plastic hood watching a videotape. The results are edited to eliminate measurement during the initial period of
acclimation to the test, and any other periods of significant physical movement or coughing. The remaining
measurements are averaged to obtain the mean REE calculated from the modified Weir equation10, using
oxygen consumption and carbon dioxide production. REE is subsequently compared to predicted values
derived from the World Health Organization that adjust for age, gender and weight11 and Schofield equations
that adjust for age, gender, weight and height12. Respiratory quotient is also obtained from the test. For infants,
sleeping energy expenditure is measured while napping following a day-time feed. The test can also be used
to assess energy expenditure under other circumstances such as the metabolic response to a meal. The
metabolic cart is somewhat portable and tests can be performed at the bedside.
Costs associated with the test are based on the research technician time required to perform the test,
process the data and provide results to the investigator, service contracts, supplies (high precision
calibration gases, replacement hoods, etc.) and replacement cost of the device.
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Tanner JM. Growth at Adolescence, (Blackwell Scientific Publication, Oxford, 1962).
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