Methods of Nutritional State Examination

Posted on Sep 14, 2024 in Medicine & Health

Methods of Examination of Nutritional State

Background

Goals of Nutritional Assessment:

  • To identify individuals or population groups at risk of becoming malnourished
  • To identify individuals or population groups who are malnourished
  • To develop health care programs that meet the community needs which are defined by the assessment
  • To measure the effectiveness of the nutritional programs & intervention once initiated

Methods:

  • Two types: direct and indirect
  • Direct methods deal with the individual and measure objective criteria, while indirect methods use community health indices that reflect nutritional influences.

Direct Methods

  • Anthropometric methods
  • Biochemical, laboratory methods
  • Clinical methods
  • Dietary evaluation methods

Indirect Methods

  • Ecological variables including crop production
  • Economic factors e.g., per capita income, population density & social habits
  • Vital health statistics, particularly infant & under 5 mortality & fertility index

Basic Evaluation

  • History and physical examination
  • History should consist of medical diagnoses, hospitalizations, changes in appetite, availability and preparation of food, medications, and details regarding weight change.
  • Weight loss is perhaps the most validated parameter of nutritional status.
  • PE: Attention should be directed toward findings of soft-tissue wasting, hydration status, evidence of vitamin and mineral deficiencies, height, weight, and BMI → hair, angles of the mouth, gums, nails, skin, eyes, tongue, muscles, bones, & thyroid gland.
  • Advantages:
    • Fast & easy to perform
    • Inexpensive
    • Non-invasive
  • Disadvantages: Can’t detect early cases

Biochemical Examinations

Main parameters: Serum proteins (albumin, transferrin, prealbumin, retinol-binding protein)

  • They are hepatically produced and negative acute-phase reactants.

Biochemical measurements are useful to assess:

  • Organ function
  • Fluid status and electrolyte balance
  • Confirm nutritional deficiencies
  • Monitor the adequacy of nutritional therapies

Advantages:

  • It is useful in detecting early changes in body metabolism & nutrition before the appearance of overt clinical signs.
  • It is precise, accurate.
  • Useful to validate data obtained from dietary methods, e.g., comparing salt intake with 24-hour urinary excretion.

Risk Factors for Malnutrition

  • Major trauma, burns, sepsis, substance abuse, recent weight loss, and many GIT disorders.
  • Additional information from the medical history can suggest possible risk factors for malnutrition.
  • Age (<18 years or >65 years)
  • Recent unintentional weight loss: < 5% in 1 month or > 10% in 6 months.
  • % weight loss = (usual body weight – current body weight)/UBW
  • Excessive alcohol intake, other substance abuse
  • Homelessness, limited access to food
  • Limited capacity for oral intake (dysphagia, odynophagia, stomatitis, mucositis)
  • Increased metabolic demands (cancer, pregnancy)
  • Nutrient losses: malabsorption syndromes, short gut syndrome, draining abscesses, etc.
  • Intake of catabolic drugs: corticosteroids, immunosuppressants, etc.
  • Protracted emesis: anorexia nervosa, bulimia, cancer chemotherapy, etc.
  • Chronic disease: AIDS, DM, CF, cancer, etc.

Anthropometric Measurements

  • Anthropometry is the measurement of body height, weight & proportions.
  • It is an essential component of clinical examination of infants, children & pregnant women.
  • It is used to evaluate both under & overnutrition.
  • The measured values reflect the current nutritional status & don’t differentiate between acute & chronic changes.
  • Other Anthropometric Measurements:
    • Mid-arm circumference:
      • It has been used for reflection of muscle protein reserves.
      • This is performed to calculate mid-upper-arm muscle area, which correlates with lean body mass.
    • Skinfold thickness:
      • It uses skinfold calipers.
      • Skinfold sites include: Triceps, Chest/Pectoral, Subscapular, Abdomen, Suprailiac, Thigh.
      • The accuracy is highly operator-dependent.
    • Head circumference
    • Head/chest ratio
    • Hip/waist ratio
  • Advantages:
    • Objective with high specificity & sensitivity
    • Measures many variables of nutritional significance (Ht, Wt, MAC, HC, skinfold thickness, waist & hip ratio & BMI).
    • Readings are numerical & gradable on standard growth charts.
    • Readings are reproducible.
    • Non-expensive & need minimal training.
  • Disadvantages:
    • Inter-observers errors in measurement
    • Limited nutritional diagnosis
    • Problems with reference standards, i.e., local versus international standards.
    • Arbitrary statistical cut-off levels for what is considered as abnormal values.

Clinical Assessment

  • Includes: subjective global assessment of nutrition (SGA) and mini-nutritional assessment (MNA).
  • Subjective Global Assessment:
    • Screening tool that categorizes nutritional status into 3 designations: “well-nourished” (grade A), “suspected malnutrition/moderately malnourished” (grade B), and “severely malnourished” (grade C).
    • It takes into account: history, physical examination, and functional capacity.
    • It has been used in most patient populations.
  • Mini-Nutritional Assessment:
    • Developed in 1989 to assess nutritional status among elderly patients (>65 years).
    • Two types: the full and short MNA.
    • The full assessment is divided into 4 groups: anthropometrics, general assessment, dietary assessment, and subjective assessment. Answers are assigned numerical values, which are added to a maximum score of 30.
      • Nutritional status is divided into 3 groups: “well-nourished” (score ≥24), “suspected malnutrition/moderately malnourished” (17-23.9), and “severely malnourished” (< 17).
    • The short-form mini-nutritional assessment (MNA-SF), initially used in low-risk community-dwelling elderly populations, is now the preferred form of MNA for all elderly patients.
      • Performed in two steps, the first step (screening) consists of 6 items strongly correlated with results from the full MNA and categorizes nutritional status as above.
      • The second step is a further assessment of those “at risk for malnutrition” or “malnourished” by screening. The MNA-SF screening score reaches a maximum of 14.

Advanced Body Composition Analysis

  • Include: dual-energy X-ray absorptiometry (DEXA), underwater (hydrostatic) weighing, air displacement plethysmography (ADP), and bioelectrical impedance analysis (BIA).
  • Dual-Energy X-ray Absorptiometry:
    • Standard for assessment of percentage of body fat and bone mineral density.
    • It has been shown to overestimate in those with a high fat percentage and to underestimate in those with a low fat percentage.
    • The machine estimates body composition in 3 compartments (fat mass, fat-free mass, and bone mineral).
  • Underwater (Hydrostatic) Weighing:
    • Criterion standard two-compartment (fat and fat-free mass) model of body composition before DEXA.
    • This method relies on the difference in body weight in air and underwater.
  • Air Displacement Plethysmography:
    • ADP uses methods similar to those of hydrostatic weighing.
    • The inverse relationship between volume and pressure (Boyle’s law) is applied for body volume determination.
    • It is as reliable as hydrostatic weighing and DEXA.
  • Bioelectrical Impedance Analysis:
    • It measures the resistance/impedance of a small electrical current as it passes through the body’s water pool.
    • Resistance to current flow is greater through adipose tissue and bone mineral than fat-free mass, as its water content is low.
    • Total body water is estimated and fat-free mass calculated based on the assumption that 73% of the body’s fat-free mass is water.
    • This method is easily performed, portable, noninvasive, and more affordable than other methods. It is generally safe, although it is not recommended in subjects with pacemakers.