Diagnosing Protein-Calorie Malnutrition
Use a two-step approach: first screen all patients with a validated tool (NRS-2002, MNA-SF, or SGA depending on population), then confirm diagnosis with specific anthropometric, laboratory, dietary intake, and functional criteria. 1
Step 1: Initial Screening
Screen all patients within 24 hours of hospital admission or when malnutrition is suspected in outpatient settings 1, 2:
- NRS-2002: Use for surgical and critically ill patients 3, 1
- MNA-SF: Use for geriatric patients, polymorbid patients, and those with cognitive dysfunction 3, 1
- SGA: Use for geriatric patients and those with gastrointestinal disease 3, 1
- GLIM criteria: Two-step approach with screening followed by comprehensive assessment 3
The NRS-2002 has high-quality evidence for identifying malnourished patients and predicting worse clinical outcomes 1.
Step 2: Diagnostic Confirmation
Once screening is positive, confirm diagnosis using the following criteria from the American Society for Parenteral and Enteral Nutrition and European Society for Clinical Nutrition and Metabolism 3, 1:
Weight Loss Criteria
- Moderate malnutrition: 5-10% weight loss within past 6 months OR 10-20% beyond 6 months 3
- Severe malnutrition: >10% weight loss within past 6 months OR >20% beyond 6 months 3
BMI Criteria (corrected for fluid retention)
For patients <70 years old 3, 1:
- Moderate: BMI <20 kg/m²
- Severe: BMI <18.5 kg/m²
For patients ≥70 years old 3, 1:
- Moderate: BMI <22 kg/m²
- Severe: BMI <20 kg/m²
Reduced Muscle Mass
Assess through validated methods including 3, 1:
- Mid-upper arm circumference (MUAC): Better than weight for patients with lower extremity edema, ascites, or large tumor masses 1
- Handgrip strength: Functional measure of muscle strength 3, 4
- CT imaging: For cancer patients to detect muscle mass loss and myosteatosis 1
Dietary Intake Assessment
Document actual food and fluid intake using semi-quantitative methods (plate diagrams) for several days 3, 1:
- Moderate reduction: Any reduction below energy requirements for >2 weeks 3, 1
- Severe reduction: ≤50% of energy requirements for >1 week 3, 1
- Intervention trigger: Food intake ≤50% of energy requirements over 3 days 3
Laboratory Markers
Prioritize short half-life proteins 3, 1:
- Prealbumin and retinol-binding protein: Better reflect recent nutritional changes than albumin 3, 1
- Total lymphocyte count: Indicator of immune function 3, 4
- Electrolytes, minerals, triglycerides: Assess metabolic status 3
Functional Assessment
Use validated scales to document functional capacity 3, 1, 4:
Critical Pitfalls to Avoid
Do Not Rely on Albumin Alone
Albumin is a negative acute phase reactant and reflects inflammation rather than nutritional status in hospitalized patients 1. Low albumin primarily indicates disease burden, not malnutrition 1.
Correct for Fluid Retention
BMI and weight are particularly poor assessment tools in patients with fluid overload 1:
- Kidney disease patients with frequent fluid overload 1
- Liver disease patients (65-90% have malnutrition but fluid retention masks weight loss) 3, 1, 4
- Heart failure patients 1
Use MUAC instead of weight in these populations 1.
Avoid Single-Parameter Diagnosis
No single test has adequate sensitivity and specificity 5. A combination of anthropometric measurements, laboratory markers, dietary intake evaluation, and functional status provides the most accurate diagnosis 1, 5.
Disease-Specific Considerations
Liver Disease
- Malnutrition present in 65-90% of end-stage liver disease patients 3, 1, 4
- Accurate nutritional assessment is difficult due to ascites and edema 4
- Dietary restrictions risk worsening malnutrition 3
Kidney Disease
- Body weight and BMI are particularly unreliable due to fluid overload 1
- NRS-2002 is the recommended screening tool 1
Cancer Patients
Monitoring Frequency
Adjust based on patient status 1: