Assessment of Nutritional Adequacy
Praveen S. Goday
A complete nutritional assessment integrates a combination of subjective medical evaluations and objective evaluation of the medical and nutritional history, including past and present dietary intake; physical examination, including anthropometric measurements and growth assessment; biochemical and metabolic parameters; and anticipation of the future medical course (including likely complications) and effects of therapy.
ROUTINE NUTRITIONAL ASSESSMENT
Nutritional assessment of an otherwise well child at a health maintenance examination differs from that of an infant or child with a chronic illness (see Chapter 10). A routine history should include a nutritional history with questions regarding family attitudes toward health foods, junk foods, dieting, fad diets, nutritional supplements, herbal remedies, and general nutrition. A healthy child on a routine visit to the doctor requires only a measurement of height, weight, and, for infants, head circumference (plotted on either the Centers for Disease Control [CDC] or World Health Organization [WHO] growth charts), along with a routine history and physical examination. If growth is normal and there are no unusual dietary habits, further assessment is not required.
Both the CDC and WHO growth charts provide meaningful data, especially when tracked over time. However, assessment of normal height and weight percentiles vary slightly when applying the 5th to 95th percentile ranges to the same children. The WHO charts are more likely to suggest shortness and overweight and are less likely to suggest underweight when compared to the CDC charts when 5th and 95th percentile cutoffs for normalcy are utilized. However, when the WHO-recommended cutoff values of z scores of –2 and +2 are applied to the WHO charts, these differences are lessened for shortness and overweight.1 The WHO charts consistently classify fewer children as underweight in early childhood years than do the CDC charts. The CDC growth charts are available at www.cdc.gov/growthcharts, and the WHO growth charts are available at www.who.int/childgrowth/standards/chart_catalogue/en/index.htm. Computer software to facilitate calculations of anthropomorphic data using the WHO charts is available at www.who.int/childgrowth/software/en.
The patient with poor growth or weight gain requires a more careful nutritional assessment. Any child with a history of poor growth or a chronic disorder placing him or her at risk for malnutrition should have periodic nutritional assessment.
MEDICAL AND NUTRITIONAL HISTORY
It is challenging to obtain an accurate nutritional history. A 24-hour recall is the most commonly used method to obtain information about a child’s intake and is useful as a screening tool. Parents and other caregivers are asked to describe the types and amounts of food eaten by the child in the previous 24-hour period. This may not represent a typical day’s intake, so the recall may not accurately describe a child’s nutrient intake, and foods consumed between meals often are not recorded. Accuracy is improved by the use of food models for estimating portion sizes, but errors are common. The 24-hour recall is helpful during clinic follow-up to measure adherence to dietary recommendations. A 3-day or 7-day food record provides a more accurate assessment of dietary intake than the 24-hour food recall. The type and quantity of intake is recorded prospectively. Analysis of these records by a pediatric dietitian provides valuable information on caloric intake and intake of specific nutrients.
The medical history may suggest inadequate intake or malabsorption. Factors that increase energy expenditure, such as fever, tachypnea, and tachycardia, should be recognized. Chronic disorders, including cardiac, endocrine, and neurologic disorders, may increase caloric utilization. Malabsorption interferes with nutrient absorption (see Chapter 408). Increased protein losses may occur through the gastrointestinal tract, skin, or kidneys.
The most useful measure of nutritional status in the healthy child or one with chronic disease is the longitudinal assessment of height and weight and correlation with normative values for age. Longitudinal assessment of height and weight is the best approach to monitoring nutritional adequacy in patients with chronic diseases. Slowing of growth will occur before specific indicators of malnutrition are apparent; however, the physical examination can identify signs of overt nutritional deficiency, including angular stomatitis, cheilosis, glossitis, wasting, and edema. Pubertal development is affected by nutritional status, and the Tanner stage of sexual development should be recorded. Measurements of temperature, heart rate, and blood pressure are important in the assessment of a child with severe malnutrition because hypothermia and bradycardia are grave prognostic signs.
Accurate measurement of the child is essential for interpretation of serial values. Infants and children should be weighed unclothed on the same scale each visit. Length should be measured on an infantometer or recumbent measurement board for children until the age of 2 years. After age 2, a stadiometer should be used for height measurement. Head size is obtained by measuring the greatest occipitofrontal circumference using a tape measure. Plotting the child’s weight, height, and head circumference on standardized growth charts allows the physician to compare the individual child to others of the same sex and age and is an indicator of chronic malnutrition (growth stunting). Weight-for-height assesses the appropriateness of an individual’s weight compared to his height, even in those patients with chronic malnutrition. Body mass index replaces the weight-for-height calculation in children older than 3 years. Ideal body weight is the weight at the 50th percentile on the weight-for-height growth chart and can be calculated from the 50th percentile of body mass index–for-age using the child’s height.
Measurement of triceps skinfold thickness and midarm circumference provide a useful estimate of adipose tissue and lean body mass respectively (see www.who.int/childgrowth/standards/en). These measurements are reliable, however, only when performed by an experienced individual such as a pediatric dietitian, and they are most useful when measured serially, being subject to intraobserver and interobserver variability. Training guides on methods of anthropometry for nutritional assessment are available at www.who.int/childgrowth/training/en.
BIOCHEMICAL ASSESSMENT OF NUTRITIONAL STATUS
Several laboratory tests may reflect nutritional status, but none alone may be considered a useful parameter of nutritional assessment. Only in the correct clinical context do any biochemical measures become useful. Hemoglobin concentration, iron, total serum proteins, albumin, transferrin, cholesterol, triglyceride, and blood levels of some vitamins may be helpful in specific disease states. Measurement of visceral proteins allows some assessment of overall nutritional adequacy. Serum albumin values vary with acute infection, trauma, or stress, and they may be abnormal because of liver or renal disease. In addition to albumin, other more rapidly metabolized proteins that may be useful to monitor nutritional status include transferrin, prealbumin, fibronectin, and retinol-binding protein.
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