What lab values are used to assess for malnutrition?

Laboratory Assessment for Malnutrition

Assess malnutrition using serum albumin (<3.5 g/dL) or prealbumin (<20 mg/dL) as your primary laboratory markers, while recognizing that albumin reflects inflammation more than pure nutritional status and must be interpreted alongside inflammatory markers like C-reactive protein. 1, 2

Core Laboratory Panel

The essential baseline laboratory assessment should include:

• Serum albumin and prealbumin are the primary visceral protein markers, though albumin has significant limitations as it reflects disease severity and inflammation rather than pure malnutrition 1, 2
• Complete blood count to assess hemoglobin and total lymphocyte count, which reflect protein status and immune function 1, 2, 3
• Comprehensive metabolic panel including electrolytes (sodium, potassium, chloride), minerals (calcium, phosphorus, magnesium), liver enzymes, and renal function tests 1, 2, 3
• Serum urea to help determine nutritional deficiencies and protein requirements 1, 3
• Triglycerides and lipid profile to assess metabolic status 1, 2

Protein Markers: Critical Interpretation

Prealbumin (transthyretin) and retinol-binding protein are superior to albumin for detecting recent nutritional changes because of their shorter half-lives, making them the quickest means of detecting nutritional improvement 1, 3

However, critical pitfalls exist:

• Hypoalbuminemia in hospitalized patients most commonly reflects acute phase response to inflammation and protein redistribution, not malnutrition 1, 2, 4
• Always measure inflammatory proteins (C-reactive protein, orosomucoids) when interpreting albumin levels to distinguish inflammation from true nutritional deficiency 1, 2
• No single protein marker is ideal as all are affected by non-nutritional physiological and pathologic states 1
• The predictive value of each individual parameter alone is insufficient—use risk scores combining multiple parameters 1

Essential Micronutrient Assessment

For patients with suspected malnutrition, measure:

• Vitamin B12 and folate to identify deficiencies causing megaloblastic anemia and neurological complications 2
• Vitamin D levels (sufficient at ≥75 nmol/L) 2
• Iron studies including serum ferritin and transferrin saturation to evaluate iron status 1, 2
• Thiamine (B1) if rapid weight loss, poor dietary intake, vomiting, alcohol abuse, edema, or neurological symptoms are present 2

Extended Micronutrient Panel for Specific Scenarios

Additional testing should be performed based on clinical presentation:

• Zinc and copper if unexplained anemia, hair loss, poor wound healing, or taste changes occur 2
• Selenium if chronic diarrhea, metabolic bone disease, unexplained anemia, or cardiomyopathy is present 2
• Vitamin A if night blindness, xerophthalmia, or protein malnutrition exists 2
• Vitamins E and K in cases of malabsorption or unexplained neuropathy 2
• Serum vitamin and trace element concentrations should be evaluated in long-term parenteral nutrition-dependent patients 1, 2

Monitoring Frequency Algorithm

For severe malnutrition or critically ill patients:

• Monitor electrolytes, glucose, and other parameters daily during initial stabilization 1, 4
• Measure body weight and serum albumin every 3 months until stabilized 2

For stable patients with chronic malnutrition:

• Repeat measurements 2-3 times per week for clinically stable children 1
• Monitor at least annually for stable adult patients 2
• Assess vitamins and trace elements every 12 months in home parenteral nutrition patients 2

Risk Stratification Tools

Rather than relying on isolated laboratory values, use validated risk scores combining multiple parameters 1:

• Prognostic inflammatory and nutritional index
• Nutritional risk index (Buzby's)
• Prognostic nutritional risk score
• Aid for decision for nutritional support score

These multidimensional tools have superior predictive value for mortality and hospitalization compared to individual lab markers 1, 5

Common Clinical Pitfalls to Avoid

• Do not attribute low albumin solely to malnutrition in hospitalized patients without assessing inflammatory markers 1, 2, 4
• Do not delay intervention to obtain extensive micronutrient panels in acutely ill patients—basic metabolic assessment is sufficient to start safely 4
• Do not interpret weight changes without assessing fluid status, as edema and ascites make weight measurements unreliable 1, 3
• Do not use transferrin alone as it shows poor correlation with nutritional status in many populations 1, 6
• Do not overlook refeeding syndrome risk based on clinical history and baseline electrolytes, particularly phosphorus, in severely malnourished patients 4