Commonly Used Nutritional Status Evaluation Indicators for Nutritional Assessment
Anthropometric indicators (such as calf circumference, subcutaneous fold thickness, etc.), fat-free mass (FFM), fat mass (FM), degree of weight loss, and whether there are other causes of anorexia (such as disease, drugs, age, etc.), biochemical indicators (albumin, etc.) are some of the commonly used nutritional status evaluation indicators.
Nutrition History
Recording the patient’s eating log (such as a 3-7-day dietary intake record) helps assess nutritional status. Also, asking the patient to recall what they ate the day before can also assist in the assessment.
Anthropometry
11.2.2.2.1 Weight and BMI
Weight and BMI are the simplest, most direct and reliable indicators in nutritional assessment that can reflect the human body’s nutritional status as a whole. A short period of weight loss is an important predictor of acute deterioration and the need for mechanical ventilation.
Assessment criteria: Malnutrition can be diagnosed as long as it meets any of the following conditions.
- 1) BMI< 18.5 kg/m .
- 2) In a definite time period, the weight loss due to non-human factors > 10%, or the weight loss within 3 months > 5%. On this basis, the diagnosis can be made according to one of the following two points:
a. BMI < 20 kg/m2 (age < 70 years old) or BMI < 22 kg/m2 (age > 70 years old).
b. FFMI < 15 kg/m2 (female) or FFMI < 17 kg/m2 (male).
11.2.2.2.2 Triceps Skinfold Thickness (TSF)
The normal reference value for this test is 8.3mm for males and 15.3mm for females. It is normal that the measured value is more than 90% of the normal value, 80%-90% is mild malnutrition, 60%-80% is moderate malnutrition, and < 60% is severe malnutrition.
11.2.2.2.3 Arm Muscle Circle (AMC)
AMC = arm circumference (cm) [TSF (mm)x0.314j
If the measured value of the upper arm muscle circumference is more than 90% of the normal value the patient is normal, 80%-90% indicates mild malnutrition, 60%-80% indicates moderate malnutrition, and < 60% indicates severe malnutrition.
11.2.2.2.4 Body Composition Measurement Method
This measurement includes the bioelectrical impedance method and dualenergy X-ray absorption measurement method.
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At present, the bioelectrical impedance method has become a widely used method for measuring and assessing the composition of the human body. This method is noninvasive easy to operate. By passing a weak AC (alternating current)signal into the human body and measuring the current impedance to analyze the body’s composition, the body fat content and muscle mass of the body can be assessed.
a. Measurement method: The tester turns on the power and inputs relevant information about the subject. The subject stands on the test bench, holds the two handles with both hands, and opens them to the side of the tester respectively, at about a 30° angle from the body. The tester then clicks the test.
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b. Observation indicators: Total water content, protein, inorganic salt, body weight (kg), body fat (BF), body fat ratio, ratio of fat distribution in waist and hip, skeletal muscle (kg), fat-free body weight, muscle mass index (BMI).
c. Advantages: Short detection time, simple operation and noninvasive. The displayed malnutrition and electrolyte changes must precede the weight change or blood biochemical change, which provides the first opportunity for clinical treatment and improves the patient’s rescue ability. At the same time, bioelectrical impedance measurement can also estimate the volume and distribution of stagnated fluid and then assess the heart, lung, and kidney systems’ functional status.
2) The dual-energy X-ray absorptiometry can accurately determine the human adipose tissue, muscle tissue, and bone density of the whole body through low-dose X-rays. This test is used for a highly accurate determination of skeletal muscle mass of limbs.
a. Measurement method: The subject must remove all metal objects on the body, lie on the measuring bed, stretch the upper limbs and lay flat on both sides of the body, with the feet slightly joined and toes pointing upward.
b. Observation indicators: Total body and bone mineral salt content, total body fat content, lean tissue content, waist and abdomen area fat content, hip area fat content, total body fat percentage, waist and abdomen area fat percentage, hip area fat percentage, waist and abdomen area fat ratio to that of the hip area. The height and weight of the subject are also measured, and BMI is calculated.
c. Advantages: Safe, convenient, low radiation absorption dose, short inspection time, etc.
Laboratory Investigations
11.2.2.3.1 Determination of Serum Protein Level
This method of measurement includes albumin, transferrin, and retinol-binding protein. The persistent presence of hypoproteinemia in patients is a reliable indicator of malnutrition, which generally reflects the nutritional status in the last 2-3 weeks. The initial measurement value of albumin below 25 g/L indicates a poor prognosis; however, due to the long half-life of albumin, it cannot be used for continuous monitoring. In contrast, the half-life of prealbumin and binding protein is short, which is better for the dynamic assessment of nutritional status and nutritional treatment efficacy. Indicators related to the nutritional status of patients with severe COVID-19 are often reduced to varying degrees. For example, the serum prealbumin level of severe COVID-19 patients is often lower than 100 g/L, and some critically severe patients are even lower than 70 g/L or even below 50 g/L.
11.2.2.3.2 Creatinine-Height Index (CHI)
CHI varies with the protein intake level and can be used to monitor the body’s nutritional status as long as the daily intake of protein is stable. CHI can reflect protein intake and the state of protein synthesis and decomposition in the body. It is closely related to total muscle mass, body surface area, and body weight and is not affected by edema and other complications. CHI of 60%-80% indicates mild protein deficiency, 40%-59% indicates moderate protein deficiency, and < 40% indicates a severe protein deficiency. Therefore, CHI can be used as a laboratory indicator for nutritional assessment in patients with normal renal function.
11.2.2.3.3 Serum Amino Acid Ratio
Serum amino acid ratio = Gly(glycine) + Ser(serine) + Glu(glutamic acid) + Leu (Ieucine)+Iso(isoleucine) + Met (methionine)+ Val(methionine) > 3 indicates malnutrition.
11.2.2.3.4 Immune Function Indicators
Indicators of immune function include the total number of lymphocytes and delayed type hypersensitivity. The total number of lymphocytes is susceptible to multiple factors, such as virus infection, immunosuppression, and hypersplenism, so it cannot accurately reflect patients’ nutritional status.
