Babette S. Zemel Virginia A. Stallings
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20 Zemel Stallings
are increasingly being used to assess bone health in children with chronic diseases. Other methods of body composition and bone density measure- ment are mainly research tools that are not read- ily applicable to the clinical setting.
Resting Energy Expenditure
Estimating daily energy needs is particularly im- portant in caring for children with varying pedi- atric diagnoses that result in undernutrition or obesity. Their energy needs are difficult to esti- mate because of variations in metabolic demands of illness and physical activity as well as the pro- portion of the body composed of lean tissue. REE accounts for 60–70% of total daily expenditure and is used to estimate total energy needs in order to achieve a specific clinical goal: weight mainte- nance, loss or gain.
Prediction equations based on age, sex, weight and length/height have been developed to esti- mate REE when direct measurement is not pos- sible. Unfortunately, these equations, derived from measurements of healthy children, do not perform well for children with serious health conditions or altered body composition. The op- timal approach is to measure REE using an indi- rect calorimeter or metabolic cart that measures oxygen consumption and carbon dioxide pro- duction.
Accurate REE measurement by indirect calo- rimetry requires standardized conditions such as early-morning testing after a night of restful sleep and an 8- to 12-hour (or age- or disease- appropriate) fast. A 40- to 60-min test enables initial environmental adjustment and exclusion of measurements during episodes of movement.
During the test, the patient should be in a quiet, awake and calm state, be in a supine position and not have performed any physical activity or re- ceived any medications known to change heart rate (such as bronchodilators). Developmentally normal children who are at least 5 years of age
typically do well while watching a movie. Infants are evaluated while sleeping. Children with de- velopmental delay often require sedation with a short-acting oral agent.
Energy needed for growth or physical activity or to support therapeutic growth acceleration must be added to the REE to estimate total energy requirements. Table 1 shows the dietary reference intake prediction equations for estimated energy requirements (kcal/day) and physical activity factors for healthy infants and children [3] . For hospitalized or ill children with less spontaneous physical activity, a factor of 1.3–1.5 × REE is a better estimate of energy needs. Additional cor- rections are made for disease severity (such as in children with cystic fibrosis) or malabsorption.
In patients who require ‘catch-up’ growth, addi- tional energy may need to be factored into the energy requirement estimation to achieve the de- sired rate of growth.
Dual-Energy X-Ray Absorptiometry
DXA is a low-energy X-ray technique (radiation exposure less than a day’s background exposure) that measures body composition and regional bone mass and density. DXA-based bone mineral content (BMC; g) and density (BMD; g/cm 2 ) measurements are important in clinical care for identifying children at risk of poor bone accrual and osteoporosis [4] . Risk factors for pediatric bone disease include immobility, malabsorption, inflammation, endocrine disturbances and use of medications known to affect bone health, such as chronic glucocorticoid therapy.
BMC or BMD values of the lumbar spine and total body (excluding the head) should be com- pared with reference values for healthy children of the same age and sex and expressed as a z-score or standard deviation (SD) score. Adjustment for height is recommended for children with altered growth [5] . A z-score of 0 is equal to the median value for the reference population of children of
Koletzko B, et al. (eds): Pediatric Nutrition in Practice. World Rev Nutr Diet. Basel, Karger, 2015, vol 113, pp 19–22 DOI: 10.1159/000367867
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the same age and sex; a z-score of –1 means the patient’s value is 1 SD below the median value for the reference population. In clinical practice, BMC or BMD z-scores between –2 and +2 are considered to be in the normal range; a BMC or BMD z-score of less than –2 is considered low for chronological age. Based on these findings and the patient’s clinical needs, the practitioner de- cides how best to increase bone accretion. Op- tions may include optimizing calcium and vita- min D in the diet, supplementing with calcium
and/or vitamin D and prescribing weight-bear- ing physical activity.
Whole-body DXA scans estimate lean body mass, fat mass and percent body fat in less than 5 min. Pediatric reference ranges are now available for percent body fat [6] as well as lean body mass index [lean body mass (kg)/height (m) 2 ] and fat mass index (kg/m 2 ) [7] . DXA body composition assessment is not regularly used in the clinical set- ting, but it may prove to be useful in the diagnosis and treatment of obesity. In cases where it is dif-
Table 1. Prediction equations for estimated energy requirements (kcal/day) and physical activity coefficients for healthy children
Infants Prediction equations 0–3 months 89 ∙ weight (kg) – 100 + 175 3–6 months 89 ∙ weight (kg) – 100 + 56 6–12 months 89 ∙ weight (kg) – 100 + 22 12–24 months 89 ∙ weight (kg) – 100 + 20
Males General prediction equation1 Sedentary PA
coefficient
Low active PA coefficient
Active PA coefficient
Very active PA coefficient 3–8 years 88.5 – 61.9 ∙ age + PAL ∙
[(26.7 ∙ weight) + 903 ∙ (height)] + 20
1.00 1.13 1.26 1.42
9–18 years 88.5 – 61.9 ∙ age + PAL ∙
[(26.7 ∙ weight) + 903 ∙ (height)] + 25
1.00 1.13 1.26 1.42
>18 years 662 – 9.53 ∙ age + PAL ∙
[(15.91 ∙ weight) + 539.6 ∙ (height)]
1.00 1.11 1.25 1.48
Overweight 3–18 years
114 – 50.9 ∙ age + PAL ∙
[(19.5 ∙ weight) + 1,161.4 ∙ (height)]
1.00 1.12 1.24 1.45
Females General prediction equation1 Sedentary PA
coefficient
Low active PA coefficient
Active PA coefficient
Very active PA coefficient 3–8 years 135.3 – 30.8 ∙ age + PAL ∙
[(10 ∙ weight) + 934 ∙ (height)] + 20
1.00 1.16 1.31 1.56
9–18 years 135.3 – 30.8 ∙ age + PAL ∙ [(10 ∙ weight) + 934 ∙ (height)] + 25
1.00 1.16 1.31 1.56
>18 years 354 – 6.91 ∙ age + PAL ∙ [(9.36 ∙ weight) + 726 ∙ (height)]
1.00 1.12 1.27 1.45
Overweight 3–18 years
389 – 41.2 ∙ age + PAL ∙ [(15 ∙ weight) + 701.6 ∙ (height)]
1.00 1.18 1.35 1.60
PA = Physical activity; PAL = PA level.
1 Each prediction equation uses weight (kg) and height (m) and requires that a PA coefficient be included in the calculation of the estimated energy requirement. The PA categories, based on PAL (calculated as the ratio of total energy expenditure to REE), are as follows: sedentary = PAL is estimated to be ≥1.0 and <1.4; low active = PAL is estimated to be ≥1.4 and <1.6; active = PAL is estima- ted to be ≥1.6 and <1.9; very active = PAL is estimated to be ≥1.9 and <2.5. Adapted from Food and Nutrition Board and Institute of Medicine [3].
22 Zemel Stallings
ficult to distinguish whether children with a high body mass index have excess adiposity, skinfold assessment can be used to make this distinction.
However, skinfold measurements by less experi- enced anthropometrists are subject to measure- ment error, and DXA assessments are more accu- rate. As DXA-based cutoff points are established for the level of body fat associated with the health risks of obesity, DXA could become a commonly used tool in the diagnosis and treatment of obesity.
Other Techniques for Assessing Body Composition
Other body composition measurement tech- niques include air displacement plethysmogra- phy (Bod Pod and Pea Pod) and bioelectrical methods such as bioelectrical impedance analyz- ers (BIA). Bod Pod, Pea Pod and BIA are current- ly not used in the clinical care of individual pa- tients who have illnesses that influence body composition and hydration. However, these methods are used in research settings to describe important changes in body composition in groups of subjects. With further research experience and the necessary healthy infant and child reference data, body composition assessment will likely move into the clinical care setting.
More advanced imaging technologies (CT and MRI) are particularly useful for measuring the composition of specific body compartments such as visceral adipose as well as intramuscular, in- tramyocellular and brown adipose tissue [2] . However, their radiation risk (CT only), availabil- ity and cost do not make them useful in clinical practice. Peripheral quantitative CT measures cross-sectional areas for fat and muscle as well as muscle density in addition to volumetric BMD of cortical and trabecular bones. However, periph- eral quantitative CT generally is not available for clinical purposes.
Conclusions
Technical measures in nutritional assessment in the clinical setting:
• include indirect calorimetry to directly mea- sure REE; the REE is used to estimate total en- ergy needs in order to achieve weight mainte- nance or gain in children;
• include DXA to measure bone mass and den- sity in children at risk of bone disease and body composition for the diagnosis and treat- ment of obesity in some settings;
• do not include Bod Pod, BIA, CT and MRI, as these are primarily research tools
X-ray absorptiometry interpretation and reporting in children and adolescents:
the 2007 ISCD Pediatric Official Posi- tions. J Clin Densitom 2008; 11: 43–58.
6 Ogden CL, Li Y, Freedman DS, Borrud LG, Flegal KM: Smoothed percentage body fat percentiles for US children and adolescents, 1999–2004. Natl Health Stat Rep 2011; 43: 1–7.
7 Weber DR, Moore RH, Leonard MB, Zemel BS: Fat and lean BMI reference curves in children and adolescents and their utility in identifying excess adipos- ity compared with BMI and percentage body fat. Am J Clin Nutr 2013; 98: 49–56.
References
1 Kaplan AS, Zemel BS, Neiswender KM, Stallings VA: Resting energy expendi- ture in clinical pediatrics: measured ver- sus prediction equations. J Pediatr 1995;
127: 200–205.
2 Zemel B: Body composition during growth and development; in Cameron N, Bogin B (eds): Human Growth and Development. Burlington, Elsevier Sci- ence, 2012, pp 462–486.
3 Food and Nutrition Board, Institute of Medicine: Dietary Reference Intakes for Energy, Carbohydrate, Fiber, Fat, Fatty Acids, Cholesterol, Protein, and Amino Acids (Macronutrients).
Washington, National Academies, 2002.
4 Bishop N, Braillon P, Burnham J, Cimaz R, Davies J, Fewtrell M, Hogler W, Ken- nedy K, Makitie O, Mughal Z, Shaw N, Vogiatzi M, Ward K, Bianchi ML: Dual- energy X-ray absorptiometry assess- ment in children and adolescents with diseases that may affect the skeleton: the 2007 ISCD Pediatric Official Positions. J Clin Densitom 2008; 11: 29–42.
5 Gordon CM, Bachrach LK, Carpenter TO, Crabtree N, El-Hajj Fuleihan G, Kutilek S, Lorenc RS, Tosi LL, Ward KA, Ward LM, Kalkwarf HJ: Dual-energy
Koletzko B, et al. (eds): Pediatric Nutrition in Practice. World Rev Nutr Diet. Basel, Karger, 2015, vol 113, pp 19–22 DOI: 10.1159/000367867
1 Specific Aspects of Childhood Nutrition
Key Words
Protein ã Vitamin ã Laboratory test ã Malabsorption ã Deficiency
Key Messages
• Identification and prevention of malnutrition is cru- cial in the ill child
• An understanding of the relationship between measures of visceral protein status and inflamma- tory responses and changes in fluid status is key to avoid misinterpretation
• The approach to evaluating vitamin deficiency should be determined by an understanding of predisposing conditions © 2015 S. Karger AG, Basel
Introduction
Laboratory tests may aid in the diagnosis of pri- mary childhood malnutrition (resulting from in- adequate intake) and are invaluable in guiding therapeutic decisions in secondary malnutrition (resulting from conditions of increased need for or losses of substrate). Because nutritional status is an independent predictor of outcome in the sick child, strict attention to indicators of visceral
protein stores and vitamin or mineral deficiencies is imperative.
Although signs and symptoms of specific nu- trient deficiencies commonly overlap and multi- ple deficiencies are frequently encountered, a ju- dicious approach to ordering laboratory tests is recommended. While a rather comprehensive list of laboratory tests is presented here, clinical sus- picion should guide the selection of specific in- vestigations. Depending on the clinical labora- tory facilities, turnaround time on certain tests may preclude their usefulness in the acute set- ting. Familiarity with these limitations will help to avoid ordering tests that do not contribute meaningfully to the management of a child. Ta- ble 1 provides a summary of the laboratory tests discussed here, including their normal values, signs and symptoms of the deficiency state, and pitfalls to avoid in their interpretation.
Protein
Assessment of visceral protein stores is commonly made by measuring serum proteins ( table 2 ), most commonly albumin, prealbumin (transthyretin) and retinol-binding protein. Interpretation of
Koletzko B, et al. (eds): Pediatric Nutrition in Practice. World Rev Nutr Diet. Basel, Karger, 2015, vol 113, pp 23–28 DOI: 10.1159/000360314
1.2 Nutritional Assessment