Laboratory Tests for Nutritional Assessment in Hospitalized Patients

Core Laboratory Tests

Serum albumin is an important marker associated with nutrition risk and can predict postoperative complications, although recent data suggests limitations as a malnutrition definer, according to the American Society for Nutrition 1, 2
Prealbumin (transthyretin) is preferred over albumin due to its shorter half-life that better reflects acute changes in nutritional status, as recommended by the American Society for Nutrition 1
Absolute lymphocyte count, along with serum albumin and Subjective Global Assessment (SGA), has been shown to accurately predict postoperative complications after abdominal surgery, as stated by the American Society for Nutrition 1
C-reactive protein (CRP) is important to measure inflammation which affects interpretation of other nutritional markers, according to the European Society for Clinical Nutrition and Metabolism 3

Albumin and prealbumin are negative acute phase reactants and decrease during inflammation, making them unreliable markers of nutritional status in acute inflammatory conditions, as noted by the American Society for Nutrition and the European Society for Clinical Nutrition and Metabolism 1, 3
In critically ill patients, trauma patients, or those with significant inflammation, albumin and prealbumin will decrease regardless of nutritional status, according to the American Society for Nutrition 4
Laboratory values should be interpreted alongside validated nutritional screening tools rather than in isolation, as recommended by the American Society for Nutrition and the European Society for Parenteral and Enteral Nutrition 2, 5

The Nutritional Risk Screening (NRS-2002), endorsed by both the European Society for Parenteral and Enteral Nutrition (ESPEN) and the American Society for Parenteral and Enteral Nutrition (ASPEN), includes BMI, weight loss, food intake, and disease severity, and is recommended for hospitalized patients 2, 5
The Subjective Global Assessment (SGA) incorporates weight change, dietary intake, GI symptoms, functional capacity, and physical examination, as recommended by the American Society for Nutrition and the European Society for Parenteral and Enteral Nutrition 2, 5
The Nutrition Risk Index (NRI) incorporates serum albumin and weight loss ratio, particularly validated in cancer patients, according to the American Society for Nutrition and the European Society for Parenteral and Enteral Nutrition 2, 5

Food intake should be monitored daily in malnourished patients using semi-quantitative methods, as recommended by the European Society for Clinical Nutrition and Metabolism 6
Insufficient food intake equal to or less than 50% of energy requirements over 3 days should trigger nutritional intervention, according to the European Society for Clinical Nutrition and Metabolism 6
Reduced food intake is one of the five criteria used in the Global Leadership Initiative on Malnutrition (GLIM) approach to diagnosing malnutrition, as stated by the European Society for Clinical Nutrition and Metabolism and the European Crohn’s and Colitis Organisation 6, 7

Do not rely solely on BMI, midarm circumference, or tissue skinfold thickness as these may not correlate with postoperative complication risk, as noted by the American Society for Nutrition 1
Avoid interpreting albumin or prealbumin in isolation without considering the patient's inflammatory status, as recommended by the American Society for Nutrition and the European Society for Clinical Nutrition and Metabolism 1, 3
Don't wait for laboratory confirmation to begin nutritional support if clinical signs of malnutrition are present, according to the European Society for Clinical Nutrition and Metabolism 6, 8

Serum electrolytes (sodium, potassium, chloride, bicarbonate) help identify nutritional deficiencies and complications, rather than diagnosing malnutrition itself, according to Clinical Nutrition 9
Elevated BUN may reflect dehydration or increased protein catabolism in severe malnutrition, as stated in Clinical Nutrition 9
Creatinine levels may be falsely low in malnourished patients due to reduced muscle mass, as reported in Clinical Nutrition 10
Glucose dysregulation requires monitoring during nutritional rehabilitation, as noted in Clinical Nutrition 9
Minerals including calcium, phosphorus, and magnesium should be assessed, as recommended in Clinical Nutrition 9
Triglycerides may be elevated or low depending on malnutrition type, according to Clinical Nutrition 9

C-reactive protein (CRP) must be measured alongside albumin/prealbumin to interpret their values correctly—elevated CRP indicates inflammation, which causes these proteins to drop regardless of nutritional status, as stated in Clinical Nutrition 11
Edema can mask weight loss and muscle wasting, as noted in Clinical Nutrition 10 and 11

Repeat laboratory tests 2-3 times per week in clinically stable patients, as recommended in Clinical Nutrition 9
Daily monitoring may be required for critically ill patients, those at refeeding syndrome risk, or newborns/infants, according to Clinical Nutrition 9
The American Journal of Kidney Diseases recommends using validated nutritional screening tools, such as Nutritional Risk Screening 2002 (NRS-2002), which includes BMI, weight loss, food intake, and disease severity 12