Nutritional assessment and nutritional risk screening represent essential components of clinical nutrition therapy. Their primary purpose is to evaluate a patient’s nutritional status and determine the degree of malnutrition using appropriate assessment methods and screening tools. These evaluations help predict actual or potential risks, including those associated with nutritional factors that may lead to unfavorable clinical outcomes. This information is used to develop tailored nutritional therapy plans aimed at enhancing patients’ clinical outcomes.
Nutritional Assessment
Nutritional assessment involves determining the nutritional status of the body and identifying the type and severity of malnutrition through clinical examinations, anthropometric measurements, biochemical testing, and composite nutritional evaluation methods. An ideal nutritional assessment approach should accurately evaluate nutritional status and predict the occurrence of nutrition-related complications and clinical outcomes.
Clinical Examination
Clinical evaluation includes collecting medical history and conducting physical examinations to determine the presence of malnutrition. The process of gathering medical history incorporates dietary surveys as well as inquiries into medical history, psychological history, medication history, and physiological functions. Dietary surveys document the types and quantities of food and beverages consumed over a specific time period to assess any changes in appetite or intake levels. Physical examinations may identify signs such as muscle atrophy, hair loss, skin damage, edema or ascites, and deficiencies in essential fatty acids and vitamins, allowing for the determination of their severity.
Anthropometric Measurements
Anthropometric evaluations provide information on body weight, fat content, and muscle mass, which are used to assess nutritional status and monitor the effectiveness of nutritional therapy. Common indicators include body weight, height, skinfold thickness, mid-upper arm circumference, and grip strength.
Body Weight
This reflects the total weight of fat tissue, lean tissues, water, and minerals, and it is one of the simplest, most direct, and reliable measures used in nutritional evaluation. Due to individual variability in body weight, changes in weight are generally used as indicators of nutritional status.
Body Mass Index (BMI)
This is widely regarded as a reliable indicator for malnutrition or obesity. The formula for BMI is as follows:
BMI = Weight (kg) / Height2 (m2)
Normal BMI values range from 18.5 to 24 kg/m2. A BMI below 18.5 kg/m2 indicates malnutrition, a BMI between 24 and <28 kg/m2 indicates overweight, and a BMI of ≥28 kg/m2 indicates obesity.
Skinfold Thickness and Mid-Arm Circumference
Triceps skinfold thickness, mid-arm circumference, and mid-arm muscle circumference measurements are used to estimate body fat and muscle mass, indirectly reflecting nutritional status.
Grip Strength
Grip strength is a valuable objective indicator for evaluating nutritional status. It correlates closely with overall nutritional health and serves as an effective measure of muscle function. Normal grip strength values are ≥35 kg in males and ≥23 kg in females.
Biochemical Tests
Plasma Proteins
Plasma protein levels provide insight into the body’s protein nutritional status and disease severity. Common indicators include albumin, prealbumin, transferrin, and retinol-binding protein. Albumin has a half-life of 18 days, so its concentration reflects long-term changes in response to nutritional therapy. Markers such as prealbumin, transferrin, and retinol-binding protein have shorter half-lives and are present in lower concentrations, making them more sensitive and effective in reflecting current nutritional status.
Nitrogen Balance
Nitrogen balance serves as a reliable indicator of protein metabolism. The formula for nitrogen balance is:
Nitrogen Balance = Nitrogen Intake - Nitrogen Loss
Positive nitrogen balance occurs when nitrogen intake exceeds nitrogen loss, indicating net protein synthesis. Negative nitrogen balance occurs when nitrogen loss surpasses intake, reflecting catabolism exceeding anabolism.
Immune Function: Total lymphocyte count is a simple and quick method for assessing cellular immune function and is applicable across all ages. Normal values range from (2.5–3.0) × 109/L, with levels below 1.8 × 109/L indicating malnutrition.
Comprehensive Nutritional Assessment Indicators
A combination of multiple assessment indicators is used to evaluate nutritional status, enhancing diagnostic sensitivity and specificity. Common comprehensive assessment methods include:
Subjective Global Assessment (SGA)
Based on medical history and physical examination, this method excludes laboratory tests and evaluates eight aspects of medical and physical history. Patients are categorized as:
- Grade A: Well-nourished.
- Grade B: Mild to moderate malnutrition.
- Grade C: Severe malnutrition.
SGA is widely used in clinical practice and is well-regarded for its predictive accuracy regarding complications, length of hospital stay, and mortality rates.
Mini Nutritional Assessment (MNA)
This is a method designed for the rapid and straightforward evaluation of nutritional status in the elderly. It involves 18 items, including anthropometric measures, general assessments, dietary questionnaires, and subjective evaluations. The final MNA score is categorized as follows:
- MNA Score ≥24: Indicates good nutritional status.
- 17 ≤ MNA Score < 24: Indicates a risk of developing malnutrition.
- MNA Score <17: Indicates confirmed malnutrition.
Body Composition Measurements
Body composition measurements provide accurate assessments of body fat, lean tissues, and cellular mass, offering insights into changes in body composition under pathological conditions. These measurements are also used for monitoring the recovery of various tissues during nutritional support, serving as a reference for developing nutritional therapy plans. Increasingly, body composition measurements are being applied in clinical practice for evaluating nutritional status. Common methods include bioelectrical impedance analysis (BIA), dual-energy X-ray absorptiometry (DEXA), computed tomography (CT), and magnetic resonance imaging (MRI).
Nutritional Risk and Nutritional Risk Screening Tools
Nutritional risk refers to the existing or potential risk, related to nutritional factors, that may contribute to unfavorable clinical outcomes in patients. This concept is closely linked to clinical outcomes and is characterized by its association with metrics such as survival rate, mortality, complications, length of hospital stay, hospitalization costs, cost-effectiveness ratio, and quality of life. Commonly used tools for nutritional risk screening include the Nutritional Risk Screening 2002 (NRS-2002) and the Malnutrition Universal Screening Tool (MUST).
Nutritional Risk Screening 2002 (NRS-2002)
NRS-2002 is the preferred tool for nutritional risk screening in hospitalized patients due to its simplicity and ease of use. It demonstrates reliable predictive value for clinical outcomes and the efficacy of nutritional support in hospitalized patients, making it widely applied in clinical practice. NRS-2002 consists of three components:
- Score for impaired nutritional status (0–3 points).
- Score for severity of disease (0–3 points).
- Age score (+1 for patients aged ≥70 years).
The overall score ranges from 0 to 7. A total score of ≥3 indicates the presence of nutritional risk, while a score of <3 indicates no nutritional risk.
Malnutrition Universal Screening Tool (MUST)
MUST consists of three components:
- BMI score (0–2 points).
- Weight loss score, reflecting weight changes (0–2 points).
- Acute disease impact score (+2 points for patients who are already unable or expected to be unable to eat for ≥5 days).
The total score is the sum of these three components, with 0 indicating low risk, 1 indicating moderate risk, and ≥2 indicating high risk. MUST has demonstrated strong predictive accuracy for metrics such as length of hospital stay, mortality, and the incidence of complications.
Diagnosis of Malnutrition
Malnutrition refers to a state of deficiency, excess, or imbalance in energy, proteins, and/or other nutrients. Undernutrition is the most common form of malnutrition in clinical practice and aligns with the conventional definition of malnutrition. It refers to a condition resulting from inadequate intake or absorption of energy, proteins, or specific nutrients, or an imbalance caused by these factors. Undernutrition may also develop due to increased nutrient consumption triggered by stress responses to diseases, trauma, or infections. Nutritional excess, on the other hand, occurs when nutrient intake exceeds requirements and accumulates in the body, leading to adverse outcomes such as obesity or other complications. Chronic overnutrition results in fat accumulation, causing obesity, which may further contribute to metabolic syndrome and various associated complications.
Malnutrition disrupts the physiological functions and structure of organs and tissues, negatively impacting clinical outcomes.
The diagnosis of malnutrition requires a comprehensive judgment based on medical history, clinical examinations, and relevant laboratory test results. Internationally recognized criteria for the diagnosis of malnutrition include:
- BMI <18.5 kg/m2.
- Unintentional weight loss accompanied by low BMI or reduced fat-free mass index (FFMI).
Unintentional weight loss refers to a decrease in body weight of >10% with no specific time constraint or a weight loss of >5% within three months, without deliberate weight control. A low BMI is defined as <20 kg/m2 for individuals under the age of 70 or <22 kg/m2 for individuals aged 70 and older. A low FFMI is defined as <15 kg/m2 for women and <17 kg/m2 for men. Meeting any one of these two criteria is sufficient for a diagnosis of malnutrition.
In recent years, the Global Leadership Initiative on Malnutrition (GLIM) has established a unified set of criteria for the assessment of malnutrition, commonly referred to as the GLIM criteria. The core of the GLIM framework divides the evaluation of malnutrition into two distinct steps: nutritional screening and diagnostic assessment.
The first step entails nutritional screening, emphasizing the use of clinically validated screening tools. The second step involves malnutrition assessment and grading of severity for patients who screen positive in step one.
The assessment includes:
Phenotypic criteria:
- Unintentional weight loss.
- Low BMI.
- Low FFMI.
Etiologic criteria:
- Reduced food intake or absorption.
- Disease burden/inflammation.
For a diagnosis of malnutrition, at least one phenotypic criterion and one etiologic criterion must be met.