Nutrition Assessment
Nutrition Assessment is the first CNSC domain and tests whether you can build a defensible nutrition diagnosis from intake, anthropometrics, biochemical data, physical findings, and functional status-not from a single laboratory value.
Use a validated malnutrition framework
The AND/ASPEN adult malnutrition criteria require at least two of: insufficient energy intake, weight loss, loss of muscle mass, loss of subcutaneous fat, localized or generalized fluid accumulation, and diminished functional status. Severity is driven by weight loss and intake: severe is often defined as >5% in 1 month or >7.5% in 3 months; moderate as 5% in 1 month or 7.5% in 3 months. GLIM uses one phenotypic criterion (weight loss, low BMI, reduced muscle mass) plus one etiologic criterion (reduced intake or inflammation). Screening tools such as MST, MUST, and NRS-2002 trigger assessment; they do not replace it.
Estimate needs with the right inputs
Mifflin-St Jeor: men 10W + 6.25H − 5A + 5; women 10W + 6.25H − 5A − 161. Use actual body weight in most adults; in obesity, use adjusted or ideal body weight for energy but actual weight for protein. Indirect calorimetry is preferred in ventilated ICU patients when available. Protein is commonly 1.2–2.0 g/kg in critical illness and 1.2–1.5 g/kg in older adults. Fluid is about 30–35 mL/kg, adjusted for heart, renal, and liver failure.
Worked example
A 68-year-old man is 175 cm, 70 kg, with 7 kg unintentional loss in 3 months (10%), CRP 45 mg/L, and 40% intake for 10 days. ASPEN severity: >7.5% loss in 3 months = severe. GLIM: weight loss plus inflammation = malnutrition. Energy at 25–30 kcal/kg = 1,750–2,100 kcal/day; protein at 1.2–1.5 g/kg = 84–105 g/day; fluid at 30 mL/kg = 2,100 mL/day. CRP supports inflammation but is not diagnostic alone.
Traps
Albumin and prealbumin are negative acute-phase proteins; do not use them alone to diagnose malnutrition. Do not accept a low BMI as the only criterion in older adults. Do not overlook edema, ascites, or obesity when selecting weight. Avoid starting 35–40 kcal/kg in a severely malnourished patient without assessing refeeding risk.