Introduction to Malnutrition Assessment
Properly assessing malnutrition is a multi-faceted process that goes beyond simple visual observation. The most widely accepted framework for diagnosing adult malnutrition is the Global Leadership Initiative on Malnutrition (GLIM) consensus. This model uses a two-step approach: first, a screening to identify individuals at risk, and second, a comprehensive assessment to diagnose and grade the severity of malnutrition. The assessment is based on a combination of phenotypic (physical) and etiologic (cause-related) criteria.
Phenotypic Criteria (Physical Signs)
Phenotypic criteria focus on tangible, physical changes to the body that signal nutritional deficiency. For an adult to be diagnosed with malnutrition under GLIM, at least one of these criteria must be met.
- Unintentional Weight Loss: This is a hallmark sign of malnutrition. The GLIM guidelines specify thresholds for diagnosing malnutrition: more than 5% weight loss over the past 6 months, or more than 10% beyond 6 months. In children, a downward trend in growth charts can also indicate a problem.
- Low Body Mass Index (BMI): BMI, calculated as weight in kilograms divided by height in meters squared ($kg/m^2$), is a standard anthropometric measure. The cutoff points for low BMI vary by age and region. For example, GLIM recommends a BMI below 20 for individuals under 70 and below 22 for those over 70, with different guidelines for Asian populations.
- Reduced Muscle Mass: Loss of muscle mass, or wasting, is a critical sign that can be assessed in several ways. While advanced imaging techniques like dual-energy X-ray absorptiometry (DXA) are ideal, physical examinations for muscle wasting and anthropometric measurements like mid-upper arm or calf circumference are also used, especially where advanced tools are unavailable.
Etiologic Criteria (Causative Factors)
In addition to physical signs, malnutrition is diagnosed by identifying underlying causes. At least one etiologic criterion must be present for a GLIM diagnosis.
- Reduced Food Intake or Absorption: This criterion considers both insufficient oral intake and issues with the body's ability to absorb nutrients. Factors can include reduced appetite, gastrointestinal problems like chronic diarrhea or vomiting, or conditions causing malabsorption.
- Inflammation or Disease Burden: The presence of inflammation, often resulting from acute injury, severe infection, or chronic illness (e.g., cancer, chronic obstructive pulmonary disease), contributes significantly to malnutrition. Inflammation can increase energy expenditure and cause muscle catabolism. Biomarkers like C-reactive protein (CRP) can be used to support this criterion.
Diagnostic Tools and Methods
Several tools and methods are used in the two-step screening and assessment process to gather the necessary data.
- Anthropometric Measurements: This includes measuring height, weight, mid-upper arm circumference (MUAC), and skinfold thickness. For children, tracking growth on standardized charts is essential.
- Biochemical Tests: Blood tests for certain proteins (e.g., albumin, prealbumin), micronutrients, and inflammatory markers (CRP) provide objective data to support a diagnosis, though many markers are affected by factors other than nutritional status.
- Dietary Assessment: A detailed dietary history helps identify inadequate nutrient intake. Tools include 24-hour recalls, food frequency questionnaires, and food diaries.
- Physical Examination: A clinical exam is crucial for observing signs of muscle and fat loss, edema, and specific micronutrient deficiencies (e.g., dry skin for vitamin A deficiency, bleeding gums for vitamin C).
- Validated Screening Tools: Initial screening can be done using validated tools like the Malnutrition Universal Screening Tool (MUST) or Mini Nutritional Assessment (MNA) for the elderly, which efficiently identify those at risk for further evaluation.
Comparing Malnutrition Assessment Criteria
| Assessment Category | GLIM Consensus | Subjective Global Assessment (SGA) | Nutritional Risk Screening 2002 (NRS-2002) |
|---|---|---|---|
| Application | Global consensus for adults in clinical settings. | Bedside clinical tool for adults. | Screening tool for hospitalized adults. |
| Key Criteria | Combines phenotypic and etiologic criteria. | History of intake, weight change, GI symptoms, and physical exam for wasting and edema. | Impaired nutritional status and disease severity; scores adjusted for age. |
| Assessment Method | Two-step: screening followed by assessment of weight loss, BMI, muscle mass, intake, and inflammation. | Clinician assesses history and physical findings to categorize as A, B, or C. | Uses scores for weight loss, BMI, and intake; disease severity based on diagnosis. |
| Main Strength | Unifies diagnostic standards globally with clear thresholds and consideration of inflammation. | Quick and comprehensive clinical evaluation that is widely validated and used. | Simple, rapid screening to identify hospitalized patients requiring further assessment. |
| Main Limitation | Some methods for measuring muscle mass are not widely available. | Requires clinical judgment, making consistency potentially variable without training. | Primarily a screening tool, not a full diagnostic assessment; relies on clinical judgement for disease severity score. |
Conclusion
Assessing malnutrition is a complex process requiring the integration of multiple criteria. The GLIM framework provides a comprehensive, globally recognized approach that combines objective physical measures (weight loss, BMI, muscle mass) with an understanding of underlying causes (inadequate intake, disease, and inflammation). By utilizing screening tools to identify at-risk individuals and following up with a detailed assessment, healthcare professionals can accurately diagnose and grade malnutrition severity. This multi-pronged strategy ensures that interventions are tailored and effective, ultimately improving patient outcomes and overall health.
