5.4 Nutrition Screening & Assessment
Key Takeaways
Nutrition screening (for example, the Malnutrition Screening Tool, MNA-SF, MUST, or NRS-2002) quickly identifies at-risk patients, and a full nutrition assessment by a registered dietitian confirms and characterizes malnutrition.
ASPEN and the Academy of Nutrition and Dietetics diagnose malnutrition when at least two of six characteristics are present: low energy intake, weight loss, loss of muscle mass, loss of subcutaneous fat, fluid accumulation, and reduced grip strength.
In chronic illness, weight loss of more than 5% in 1 month, more than 7.5% in 3 months, more than 10% in 6 months, or more than 20% in 1 year, or intake of 75% or less of needs for at least 1 month, supports severe malnutrition.
Albumin and prealbumin fall with inflammation, infection, and fluid shifts, so ASPEN advises against using them to diagnose malnutrition or track repletion; interpret them alongside C-reactive protein and clinical findings.
The GLIM criteria require at least one phenotypic criterion (unintentional weight loss, low BMI, or reduced muscle mass) plus one etiologic criterion (reduced intake or assimilation, or inflammation and disease burden).
5.4 Nutrition Screening & Assessment
Core Clinical Principle: Malnutrition slows every phase of healing, yet it is easy to miss in patients who are overweight or whose laboratory values are distorted by inflammation. A good assessment relies on weight history, intake, and a physical examination for muscle and fat loss rather than on serum proteins alone.
The CWSP outline lists nutrition in both Assessment and Diagnosis and Patient Management, and addressing nutritional deficits is a listed task. This section covers identifying and diagnosing malnutrition; nutrition therapy is covered separately.
Step 1: Screening
Screening is quick, done by any trained staff member, and repeated regularly (on admission and when the condition changes).
| Tool | Setting | Content | At-Risk Result |
|---|---|---|---|
| Malnutrition Screening Tool (MST) | Hospitals, clinics | Recent unintentional weight loss and poor appetite | Score of 2 or more |
| Mini Nutritional Assessment-Short Form (MNA-SF) | Older adults in all settings | Intake decline, weight loss, mobility, acute stress, neuropsychological problems, BMI or calf circumference | 12–14 normal; 8–11 at risk; 0–7 malnourished |
| Malnutrition Universal Screening Tool (MUST) | Community and hospital | BMI, unplanned weight loss, acute disease effect | 1 medium risk; 2 or more high risk |
| Nutritional Risk Screening 2002 (NRS-2002) | Hospital inpatients | Nutritional status plus disease severity, age adjustment | 3 or more at risk |
Patients who screen positive, and all patients with pressure injuries or other chronic wounds at nutritional risk, should have a full assessment by a registered dietitian.
Step 2: Assessment and Diagnosis
ASPEN and Academy of Nutrition and Dietetics Characteristics
Malnutrition is diagnosed when two or more of these six characteristics are present, and severity depends on the setting (acute illness, chronic illness, or social or environmental circumstances):
| Characteristic | Severe Malnutrition in Chronic Illness |
|---|---|
| Energy intake | 75% or less of estimated needs for at least 1 month |
| Weight loss | More than 5% in 1 month, more than 7.5% in 3 months, more than 10% in 6 months, or more than 20% in 1 year |
| Loss of subcutaneous fat | Severe (for example, orbital, triceps, and rib areas) |
| Loss of muscle mass | Severe (for example, temples, clavicles, shoulders, interosseous muscles, calves) |
| Fluid accumulation | Severe, which can mask weight loss |
| Grip strength | Measurably reduced |
For moderate malnutrition in chronic illness, the thresholds are intake below 75% of needs for at least 1 month and weight loss of 5% in 1 month, 7.5% in 3 months, 10% in 6 months, or 20% in 1 year, with mild fat or muscle loss. In acute illness, the time frames are shorter (for example, severe malnutrition includes intake of 50% or less for at least 5 days, or weight loss of more than 2% in 1 week).
GLIM Criteria
The Global Leadership Initiative on Malnutrition (GLIM) requires one phenotypic and one etiologic criterion:
- Phenotypic: Unintentional weight loss (more than 5% within 6 months or more than 10% beyond 6 months), low BMI (below 20 kg/m² if younger than 70 years, below 22 kg/m² if 70 or older, with lower cutoffs for Asian populations), or reduced muscle mass.
- Etiologic: Reduced food intake or assimilation, or inflammation related to acute disease, injury, or chronic disease.
Nutrition-Focused Physical Examination
Look for temporal hollowing, prominent clavicles and scapulae, squared shoulders, wasting of the hand interosseous muscles, thin calves, loss of fat around the eyes and triceps, edema that masks weight loss, and signs of micronutrient deficiency such as perifollicular hemorrhages and corkscrew hairs (vitamin C), angular cheilitis and glossitis (B vitamins, iron), and periorificial dermatitis (zinc).
Step 3: Interpreting Laboratory Tests
| Test | Useful For | Caution |
|---|---|---|
| Albumin (half-life about 20 days) | Overall illness severity and prognosis | Falls with inflammation, liver disease, fluid overload, and protein-losing states; not a malnutrition marker |
| Prealbumin (transthyretin) (half-life 2–3 days) | Inflammation trends | Falls with inflammation and rises with kidney failure and steroids; ASPEN advises against using it to diagnose malnutrition or track repletion |
| C-reactive protein | Shows whether inflammation explains low albumin or prealbumin | Nonspecific |
| Glucose and HbA1c | Glycemic control | HbA1c is less reliable with anemia, transfusion, and kidney failure |
| BUN, creatinine, sodium, osmolality | Hydration status; a BUN-to-creatinine ratio above about 20 suggests volume depletion | Affected by bleeding, steroids, and kidney disease |
| Micronutrients (vitamin C, zinc, vitamin D, iron studies, B12, folate) | Confirming suspected deficiency | Zinc and iron fall during inflammation; test when clinically suspected, not routinely |
| Hemoglobin | Oxygen-carrying capacity | Anemia has many causes beyond nutrition |
Special Situations
- Obesity: Patients with obesity can be malnourished, and sarcopenic obesity combines excess fat with low muscle mass. Rely on weight history, intake, and muscle assessment, not BMI.
- Edema and ascites: Fluid hides weight loss; use dry-weight estimates and the physical exam.
- After bariatric surgery: Watch for protein, iron, B12, thiamine, copper, zinc, and fat-soluble vitamin deficiencies.
- Hydration: Older adults often have blunted thirst; dehydration reduces skin turgor and tissue perfusion.
Clinical Traps
Trap 1: Diagnosing Malnutrition From a Low Albumin
A patient with an infected wound and a CRP of 150 mg/L will have a low albumin whether or not he is malnourished. Base the diagnosis on intake, weight change, and the physical exam.
Trap 2: Missing Malnutrition in a Patient With Obesity
A BMI of 34 kg/m² does not exclude a 12% weight loss over 6 months and muscle wasting.
A 72-year-old man with a chronic venous leg ulcer and heart failure reports eating about two-thirds of his usual meals for the past 6 weeks. His weight fell from 80 kg to 73 kg over 3 months. Examination shows mild temporal wasting and reduced grip strength. According to ASPEN and Academy of Nutrition and Dietetics criteria for chronic illness, how should his nutrition status be classified?
No malnutrition, because only one characteristic is present.
Moderate malnutrition, because weight loss of 5% in 1 month is the only criterion met.
Severe malnutrition in the context of chronic illness, based on weight loss of more than 7.5% in 3 months and intake of 75% or less of needs for at least 1 month, with supporting muscle and grip findings.
Malnutrition cannot be assessed without a prealbumin level.
A 58-year-old woman is admitted with a moderate diabetic foot infection. Her albumin is 2.6 g/dL, prealbumin is 9 mg/dL, and C-reactive protein is 142 mg/L. Her weight is stable and she reports eating her usual diet until 3 days ago. What is the best interpretation of these laboratory values?
They prove severe protein-calorie malnutrition that requires parenteral nutrition.
They indicate that she will not heal and that amputation is inevitable.
They show that her wound healing is complete and supplements are unnecessary.
They mainly reflect the acute inflammatory response to infection, so malnutrition should be judged by intake, weight history, and physical examination, while the low albumin still signals illness severity.
An 84-year-old woman in a skilled nursing facility has a stage 3 pressure injury. Her Mini Nutritional Assessment-Short Form score is 6. What does this result indicate, and what should happen next?
It indicates malnutrition (a score of 0–7), so she should have a full nutrition assessment by a registered dietitian and an individualized nutrition plan.
It indicates normal nutrition status (a score of 12–14), so no action is needed.
It indicates that she is at risk (a score of 8–11), so she should be rescreened in 1 year.
It is invalid in patients with pressure injuries, so only serum albumin should be used.
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