Chapter 072. Malnutrition and Nutritional Assessment (Part 6) Anthropometrics Anthropometric measurements provide information on body muscle mass and fat reserves. The most practical and commonly used measurements are body weight, height, triceps skinfold (TSF), and mid-arm muscle circumference (MAMC). Body weight is one of the most useful nutritional parameters to follow in patients who are acutely or chronically ill. Unintentional weight loss during illness often reflects loss of lean body mass (muscle and organ tissue), especially if it is rapid and not caused by diuresis. This can be an ominous sign since it indicates use of vital body protein stores as a metabolic fuel. The reference standard for normal body weight, body mass index (BMI, or weight in kilograms divided by height, in meters, squared), is discussed in Chap 75. BMIs <18.5 are considered underweight, 18.5–24.9 are normal, 25–29.9 are overweight, and ≥30 are obese. Measurement of skinfold thickness is useful for estimating body fat stores, because about 50% of body fat is normally located in the subcutaneous region. Skinfold thicknesses can also permit discrimination of fat mass from muscle mass. The TSF is a convenient site that is generally representative of the body's overall fat level. A thickness of <3 mm suggests virtually complete exhaustion of fat stores. The MAMC, often used to estimate skeletal muscle mass, is calculated as follows: Laboratory Studies A number of laboratory tests used routinely in clinical medicine can yield valuable information about a patient's nutritional status if a slightly different approach to their interpretation is used. For example, abnormally low serum albumin levels, total iron-binding capacity, and anergy may have a distinct explanation, but collectively they may represent kwashiorkor. In the clinical setting of a hypermetabolic, acutely ill patient who is edematous and has easily pluckable hair and inadequate protein intake, the diagnosis of kwashiorkor is clear-cut. Commonly used laboratory tests for assessing nutritional status are outlined in Table 72-5. The table also provides tips to help avoid assigning nutritional significance to tests that may be abnormal for nonnutritional reasons. Table 72-5 Laboratory Tests for Nutritional Assessment Test (Normal Values) Nutritional Use Causes of Normal Value Despite Malnutrition Other Causes of Abnormal Value 2.8–3.5: Compromised protein status Dehydratio n Low <2.8: Possible kwashiorkor Infusion of albumin, fresh frozen plasma, o r whole blood Common: Serum albumin(3.5–5.5 g/dL) Increasing value reflects positive protein Infection and other stress, especially with poor protein balance intake Burns, trauma Congestive heart failure Fluid overload Severe liver disease Uncommon: Nephrotic syndrome Zinc deficiency Bacterial stasis/overgrowth of small intestine 10–15 mg/dL: Mild protein depletion Chronic renal failure Similar to serum albumin 5– 10 mg/dL: Moderate protein depletion <5 mg/dL: Severe protein depletion Serum prealbumin, also called transthyretin (20– 40 mg/dL; lower in prepubertal children) Increasing value reflects positive protein balance <200: Compromised prote in status, possible kwashiorkor Iron deficiency Low Increasing value reflects positive protein balance Similar to serum albumin More labile than albumin High Serum total iron binding capacity (TIBC) 240–450 µg/dL Iron deficiency Prothrombi n time 12.0– 15.5 sec Prolongation : vitamin K deficiency Prolonged Anticoagulant therapy (warfarin) Severe liver disease <0.6: Muscle wasting due to prolonged energy deficit High Reflects muscle mass Despite muscle wasting: Renal failure Serum creatinine 0.6– 1.6 mg/dL Severe dehydration 24- h urinary creatinine 500– Low value: muscle wasting due >24-h Low collection to prolonged energy deficit Decreasing serum creatinine Incomplete urine collection Increasing serum creatinine 1200 mg/d (standardized for height and sex) Neuromuscular wasting 24- h urinary urea nitrogen (UUN) <5 g/d (depends on level of protein intake) Determine level of catabolism (as long as protein intake is ≥10 g below calculated protein loss or <20 g total, but at least 100 g carbohydrate is provided) 5– 10 g/d = mild catabolism or normal fed state 10– 15 g/d = moderate catabolism >15 g/d = severe catabolism Estimate protein balance Protein balance = protein intake – protein loss where protein loss (protein catabolic rate) = [24- h UUN (g) + 4] x 6.25 Adjustments required in burn patients and others with large nonurinary nitrogen losses and in patients with fluctuating BUN levels (e.g., renal failure) <8: Possibly inadequ ate protein intake Low Blood urea nitrogen (BUN) 8– 23 mg/dL 12–23: Possibly adequate protein intake Severe liver disease . Chapter 072. Malnutrition and Nutritional Assessment (Part 6) Anthropometrics Anthropometric measurements provide information on body muscle mass and fat reserves. The most practical and. avoid assigning nutritional significance to tests that may be abnormal for nonnutritional reasons. Table 72-5 Laboratory Tests for Nutritional Assessment Test (Normal Values) Nutritional Use. patient who is edematous and has easily pluckable hair and inadequate protein intake, the diagnosis of kwashiorkor is clear-cut. Commonly used laboratory tests for assessing nutritional status are