9. Assessment of nutritional status, nutritional screening

Tools in the assessment of nutritional status – anthropometric measurements

• Anthropometry
  • = measurement of height, weight, and proportions of a person
  • Especially used in infants, children, pregnant
  • Advantages of anthropometry
    • High specificity, high sensitivity
    • Many variables are acquired and measured
    • Data can be graded on charts and compared to healthy subjects
  • Disadvantages of anthropometry
    • Difference in measurements depending on the observer
    • Gives limited information on specific nutritional state
• Anthropometry in children
  • Used to evaluate the child’s growth relative to what’s normal for its gender and age
• Body mass index – BMI
  • Defined as the weight (kg) divided by the height squared (m2)
  • High BMI – associated with type 2 diabetes and mortality
  • Classification
    • BMI < 18.5 – underweight
    • BMI 18.5 – 25 – normal range
    • BMI 25 – 30 – overweight (pre-obesity)
    • BMI 30 – 35 – obese (grade 1 obesity)
    • BMI 35 – 40 – severely obese (grade 2 obesity)
    • BMI > 40 – morbidly obese (grade 3 obesity)
  • Proportion of obese vs non-obese people in the western world has increased the last decades
• Waist circumference
  • Predicts mortality better than any other anthropometric measurement
  • Can be used to assess obesity
  • Measured at the level of the umbilicus, rounded to nearest 0.5 cm
  • Two risk levels exist according to waist circumference
    • Level 1 – males – circumference > 94 cm
    • Level 2 – males – circumference > 102 cm
    • Level 1 – females – circumference > 80 cm
    • Level 2 – females – circumference > 88 cm
• Hip circumference
  • Measured at the point of greatest circumference around the hips, rounded to nearest 0.5 cm
• Waist/hip ratio
  • Waist circumference divided by hip circumference
  • Defined as central obesity if ratio > 0.95 in males or > 0.80 in females
• Skin fold thickness
  • A special tool measured the thickness of a fold of skin
  • Can be used to estimate the body fat percentage
  • Very cheap, not very accurate
  • Common sites to measure skin fold thickness:
    • Triceps
    • Abdomen
    • Frontal thigh
    • Chest
• Hydrostatic weighing
  • By lowering a person into a pool of water and measuring how much water is displaced, we can find out the volume and therefore the density of the person
  • The density can be used to estimate the body fat percentage
  • Expensive, time-consuming, but very accurate
• Bioelectrical impedance analysis
  • A machine measures the resistance (impedance) of the body and estimates the body fat percentage
  • Not time-consuming, relatively expensive but not very accurate

Biochemical methods of assessment of nutritional state

• Advantages of biochemical methods
  • Can detect changes early, perhaps before clinical symptoms
  • Accurate measurements
• Disadvantages of biochemical methods
  • Time consuming
  • Expensive
  • Requires trained personnel
• Biomarkers of nutritional state
  • Serum haemoglobin
    • Decreased in anaemia, protein deficiency or mineral deficiency
  • Stool examination
    • Presence of intestinal parasites can be seen
  • Urine dipstick
    • Can detect blood, sugar, albumin
  • Urinary levels of minerals like potassium, sodium, fluoride, chloride, iodide
    • Reflects the recent intake of minerals
  • Level of nutrients in RBCs, adipose tissue, nails, hair
    • Reflects dietary intake over weeks or months
  • Cholesterol esters in RBC membrane
    • Reflect recent lipid intake
  • Transferrin levels
    • Reflect protein intake in last week
  • HbA1c
    • Reflects average blood glucose level last 3 months

Clinical assessment of nutritional state

• Advantages of clinical assessment
  • Simple, most practical method
  • Non-invasive
• Disadvantages of clinical assessment
  • Can’t detect early
  • Detected signs aren’t specific to certain dietary component
• Examination of areas like
  • Hair
    • Abnormal in protein, zinc, vitamin A, vitamin C deficiency
  • Nails
    • Abnormal in iron, protein deficiency
  • Skin
    • Abnormal in iron, folate, vitamin C, vitamin B2, vitamin A, zinc deficiency
  • Angle of mouth
    • Abnormal in iron, vitamin B deficiency
  • Gums
    • Bleeding in vitamin C deficiency
  • Tongue
  • Eyes
  • Thyroid gland
    • Enlarged in iodine deficiency
  • Muscles
  • Bones
    • Abnormal in vitamin D and vitamin C deficiency

Dietary assessment of nutritional state

• Methods
  • Dietary recall – subject is asked to list foods consumed during a certain period of time, usually in the last 24 hours
    • Quick, simple
    • Depends on short term memory
    • Doesn’t represent usual intake
  • Food diary – subject writes a record of their intake as they eat
    • Needs cooperation of the individual
  • Food frequency questionnaire – subject is given a questionnaire that ask how often they consume a certain food
    • Example: How many times a week do you eat bread?
    • It’s easy to forget or underreport certain food habits
  • Diet histories – subject is simply asked open-ended questions regarding their usual food habits
    • Time consuming
    • It’s easy to forget or underreport certain food habits
  • Observed food consumption
• Interpreting results
  • Quantitative interpretation – calculating the amount of energy and specific nutrients the patient consumes and compare it to the recommendations
    • Time-consuming
  • Qualitative interpretation – comparing the different food groups the patient eats with the food groups of a recommended diet

Indirect methods of nutritional assessment

• Ecological variables, like crop production
• Economic factors
  • Income per capita
  • Population density
  • Social habits
• Vital health statistics
  • Infant mortality
  • Fertility index