View source for 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

[[Category:Public health 4 - Preventive medicine]]