From the Guidelines
Laboratory tests to evaluate malnutrition should include a combination of serum albumin, prealbumin, transferrin, total protein, complete blood count, electrolytes, and micronutrient levels, with a strong emphasis on interpreting these tests together with clinical findings and considering the potential impact of inflammation on protein levels, as recommended by the most recent guidelines 1. When evaluating malnutrition, it is essential to consider the limitations of each laboratory test, as no single protein is ideal as an indicator of nutritional status due to the influence of non-nutritional physiological and pathologic states 1. Some key laboratory tests that can be used to evaluate malnutrition include:
- Serum albumin, which is the most commonly used marker, although its half-life of 20 days makes it less responsive to acute changes
- Prealbumin (transthyretin), which has a shorter half-life of 2-3 days and provides better assessment of recent nutritional status
- Transferrin, which has a half-life of 8-10 days and can help evaluate protein status
- Complete blood count, which may reveal anemia from iron, folate, or B12 deficiencies
- Specific micronutrient testing, such as vitamins A, D, B12, folate, zinc, and iron, which should be ordered based on clinical suspicion
- Nitrogen balance studies, which can assess protein metabolism by measuring nitrogen intake versus excretion
- C-reactive protein, which should be measured alongside these markers to account for the potential impact of inflammation on protein levels, as recommended by the espen micronutrient guideline 1. In addition to these laboratory tests, clinical findings such as weight loss, muscle wasting, and functional status should also be considered for a comprehensive malnutrition assessment. The frequency of laboratory testing may vary depending on the patient's condition, with daily monitoring required for newborns, infants, critically ill patients, and those at risk of refeeding syndrome, while clinically stable children may require measurements 2-3 times per week 1.
From the Research
Malnutrition Evaluation Labs
To evaluate malnutrition, several laboratory markers and assessment tools can be used.
- Serum visceral proteins such as albumin and prealbumin have traditionally been used as markers of nutritional status 2
- Prealbumin is often preferred over albumin due to its shorter half-life, reflecting more rapid changes in nutritional state 2
- Other markers of nutritional status, such as urinary creatinine or 3-methylhistidine, have not found widespread use 2
- Serum IGF-1 is less influenced by inflammation and falls during malnutrition, but its concentration changes are not sufficiently specific to be useful clinically as a marker of malnutrition 2
Malnutrition Diagnostic Tools
Several malnutrition diagnostic tools are currently in use, including:
- Subjective Global Assessment
- Mini Nutritional Assessment
- Academy of Nutrition and Dietetics/American Society for Parenteral and Enteral Nutrition malnutrition consensus characteristics
- Global Leadership Initiative on Malnutrition criteria 3 These tools can help clinicians choose their approach in diagnosing malnutrition and identifying a core data set to evaluate malnutrition prevalence globally 3
Nutritional Screening and Assessment
Nutritional risk screening is conducted using simple, quick-to-perform tools, and is the first line of action in detecting at-risk patients 4
- This should be implemented systematically and periodically on admission to hospital or residential care, as well as on an outpatient basis for patients with chronic conditions 4
- Once patients with a nutritional risk are detected, they should undergo a more detailed nutritional assessment to identify and quantify the type and degree of malnutrition 4
- This assessment should include health history and clinical examination, dietary history, anthropometric measurements, evaluation of the degree of aggression determined by the disease, functional assessment, and, whenever possible, some method of measuring body composition 4
Types of Malnutrition
There are three types of malnutrition: