What are the methods to identify malnutrition?

How to Identify Malnutrition

Use a two-step approach: first perform systematic screening with a validated tool (NRS-2002, MUST, or MST), then conduct comprehensive assessment in screen-positive patients using the ESPEN or ASPEN/Academy criteria to confirm the diagnosis. 1

Step 1: Systematic Screening (First-Line Detection)

All patients should be screened at hospital admission, in residential care facilities, and periodically in outpatient settings for chronic conditions. 1, 2

Validated Screening Tools

Choose one of these evidence-based tools:

• NRS-2002: Endorsed by ESPEN; validated for surgical and critically ill patients; independently predicts postoperative complications and mortality 1
• MUST (Malnutrition Universal Screening Tool): Quick assessment based on BMI, unplanned weight loss, and acute disease effect 1
• MST (Malnutrition Screening Tool): Focuses on unintentional weight loss and poor appetite; does not rely on low BMI; received "good/strong" rating 1
• Renal iNUT: Specifically developed for hospitalized patients with kidney disease; includes appetite, dietary intake, and dry-weight considerations 1

For geriatric patients, screen every 3 months in stable long-term care residents and at least annually in general practice. 1

Step 2: Comprehensive Assessment (Confirming Diagnosis)

Once screening identifies at-risk patients, perform detailed assessment using either ESPEN or ASPEN/Academy diagnostic criteria. 1

ESPEN Diagnostic Criteria (2017)

Diagnosis requires fulfilling nutritional risk screening PLUS one of these two options: 1

Option A: BMI <18.5 kg/m²

Option B: Combined findings of:

• Weight loss:

  • 10% unintentional weight loss (indefinite timeframe), OR

  • 5% unintentional weight loss in past 3 months

• PLUS age-dependent low BMI:
  • <20 kg/m² if age <70 years
  • <22 kg/m² if age ≥70 years
• OR reduced fat-free mass index (FFMI): <15 kg/m² (women) or <17 kg/m² (men) 1

ASPEN/Academy Diagnostic Criteria

Diagnosis requires at least 2 of these 6 criteria: 1

1. Insufficient energy intake
2. Weight loss
3. Loss of muscle mass
4. Loss of subcutaneous fat
5. Localized or generalized fluid accumulation
6. Diminished handgrip strength 1

Essential Assessment Components

Medical and dietary history: 1, 2

• Unintentional weight loss (quantify percentage and timeframe)
• Recent dietary intake patterns (quantitative food records preferred)
• Gastrointestinal symptoms (nausea, vomiting, diarrhea, constipation, malabsorption)
• Nutrition impact symptoms (anorexia, changes in taste/smell, dysphagia, pain)
• Underlying diseases and inflammatory conditions
• Medications affecting nutritional status

Physical examination (Nutrition-Focused Physical Exam): 3

• Muscle mass assessment: Temporal wasting, clavicular prominence, shoulder/scapular definition, interosseous muscle wasting, quadriceps/calf muscle loss
• Fat stores evaluation: Orbital fat pads, buccal fat, subcutaneous fat at triceps and lower ribs
• Fluid accumulation: Ankle/sacral edema, ascites, pleural effusion
• Micronutrient deficiency signs: Hair changes, skin abnormalities, nail changes, oral cavity findings
• Functional capacity: WHO/ECOG performance status (0-4) or Karnofsky scale (0-100) 1

Anthropometric measurements: 1, 2

• Weight and height (calculate BMI)
• Correct weight for fluid overload (edema, ascites, pleural effusion) 1
• Mid-upper arm circumference (MUAC) - particularly useful when lower extremity edema or ascites present 1
• Triceps skinfold thickness
• Calculate mid-arm muscle area from MUAC and skinfold 1

Body composition assessment (when available): 1

• DEXA scan
• CT scan at L3 vertebra for skeletal muscle index
• Bioelectrical impedance analysis (BIA)
• Fat-free mass index measurement 1

Laboratory evaluation: 4, 5, 6

Core panel:

• Complete blood count (hemoglobin, total lymphocyte count)
• Comprehensive metabolic panel (electrolytes, liver enzymes, renal function)
• Serum albumin PLUS C-reactive protein (to distinguish inflammation from true nutritional deficiency) 5, 6
• Prealbumin or retinol-binding protein (superior for detecting recent nutritional changes due to shorter half-lives) 4, 5, 6
• Serum urea (assess protein requirements)
• Triglycerides and lipid profile 5

Micronutrient assessment (initial panel): 5, 6

• Vitamin B12 and folate
• Vitamin D (sufficiency ≥75 nmol/L)
• Iron studies (ferritin, transferrin saturation)

Extended micronutrient testing (based on clinical context): 5

• Zinc and copper (if anemia, hair loss, poor wound healing, taste changes)
• Selenium (if chronic diarrhea, cardiomyopathy)
• Thiamine (if rapid weight loss, vomiting, alcohol abuse, neurological symptoms)
• Vitamins A, E, K (if malabsorption, night blindness, neuropathy)

Functional assessment: 1

• Handgrip strength measurement (dynamometer)
• Walking tests
• Activities of daily living evaluation

Step 3: Classify Malnutrition Type

After confirming diagnosis, classify by etiology to guide treatment: 1

1. Disease-related malnutrition WITH inflammation: Acute disease/injury or chronic disease with inflammatory response 1
2. Disease-related malnutrition WITHOUT inflammation: Organ failure, pancreatic insufficiency, malabsorption 1
3. Malnutrition WITHOUT disease: Starvation, socioeconomic factors, anorexia nervosa 1

Critical Pitfalls to Avoid

Do not rely on albumin alone - it reflects inflammation and disease severity more than pure nutritional status; always measure alongside CRP or other inflammatory markers 4, 5, 6

Do not interpret weight changes without assessing fluid status - edema, ascites, and pleural effusions make weight measurements unreliable 1, 5

Do not use BMI alone in overhydrated patients - particularly problematic in kidney disease and liver disease with ascites 1

Do not overlook malnutrition in overweight/obese patients - malnutrition can coexist with obesity, especially with inflammatory conditions 1

Do not use transferrin alone - shows poor correlation with nutritional status in many populations 5

Special Population Considerations

Kidney disease patients: Use Renal iNUT screening tool; BMI has limited utility due to fluid retention; monitor body weight and albumin every 3 months if GFR <30 mL/min/1.73m² 1, 5

Cancer patients: Assess systemic inflammation using modified Glasgow Prognostic Score (CRP + albumin); evaluate nutrition impact symptoms; measure muscle mass via CT at L3 1

Geriatric patients: Screen every 3 months in stable residents; use SGA or MNA-SF; consider cognitive dysfunction impact on dietary intake 1

Critical care patients: Use mNUTRIC score; monitor daily initially; assess for refeeding syndrome risk 1

Monitoring Frequency

Severe malnutrition or critically ill: Daily monitoring of electrolytes and glucose during initial stabilization 5, 6

Stable chronic malnutrition: Every 3 months (body weight and serum albumin minimum) until stabilized 5, 6

Long-term parenteral nutrition: Measure trace elements and vitamins at 12-month intervals 5