Biochemical and functional tests can be used to assess nutritional status. Biochemical tests measure nutrients or their metabolites in biological samples like blood, urine, or tissues. They are useful for detecting later-stage deficiencies when body levels are depleted. Functional tests measure enzyme activities or physiological changes related to a nutrient. Both types of tests aim to be sensitive, specific, easy to perform, non-invasive, and inexpensive. Common biochemical tests include hemoglobin for iron status and serum retinol for vitamin A. Cut-off levels are used to define deficiencies for many nutrients based on biochemical indicators. Functional tests are less often used for large surveys due to invasiveness and difficulty interpreting results.

1. Biochemical
Assessment
Md . Sajib Reza
Lecturer
Department of Food technology and Nutritional Science
Mawlana Bhashani Science and Technology university
Tangail-1902, Bangladesh
Email: sajib.ftns2010@gmail.Com

2. Biochemical or Laboratory methods … …
Include both static biochemical and functional tests. (two types)
 Biochemical tests: measures, biological fluids or tissues or the urinary excretion rate of the
nutrient or its metabolite. (e.g. plasma, serum, blood, urine, erythrocyte, leukocytes, hair,
nails, muscle, bone test)
Useful for identifying the second and third stages in the development of a nutritional
deficiency
 When the body fluid levels, become gradually depleted of the nutrient
 Biochemical changes can be expected to occur prior to clinical manifestations.
 conducted on easily accessible body fluids such as blood and urine
 Help to diagnose disease at the subclinical stage
 Confirm clinical diagnosis at the disease stage because Clinical signs and symptoms may
non-specific.
An ideal biochemical test should be –
֍ sensitive, ֍ specific, ֍ easy to carry out, ֍ non-invasive, ֍ preferably inexpensive
֍ should reveal information on the extent of tissue unsaturation rather than short-term
fluctuations in the diet.

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Functional tests: measuring the production of an abnormal metabolite or changes
in the activities of certain enzymes/ blood components, depending on a specific
nutrient
• It is done by following ways:
• Measurement of enzymatic activities specific to the particular nutrient.
• abnormal metabolites Production
• Physiological or behavioral functions.
 Include Functional physiological or behavioral tests
 Used to detect the later stages in the development of a nutritional deficiency
 Functional physiological tests are not suitable for large scale nutrition surveys
They are often too invasive, they may require elaborate equipment
 Results are difficult to interpret because of the lack of cut off points
 Less responsive than biochemical tests
e.g. Electrocardiogram (ECG), Urea breath test, Respiratory function test,
Neurophysiological tests etc.

4. Mostly used biochemical methods:
For determination of Vitamin A
status:
Serum vitamin A concentration,
Relative dose response (RDR) test,
Modified relative dose response (MRDR)
test
Plasma retinol binding protein response
test
For determination of Iron status:
Hemoglobin concentration,
serum iron concentration,
total iron binding capacity (TIBC),
erythrocyte (RBC)
protoporphyrin,
transferring saturation

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Serum Retinol:
• serum concentration is not a reliable
indicator to use for diagnosing vitamin
A deficiency in individuals.
• A disadvantage is that retinol
concentrations are decreased by acute
and underlying chronic infections.
• Prevalence of serum values of vitamin
A ≤ 0.70 µmol/l in children ≥ 1 year
Vitamin D:
• Most accepted indicator - serum levels
of vitamin D metabolite, 25-hydroxy
cholecalciferol (25 HOC).
• guidelines are -
> 10 ɳg/ ml (25 nmoles/L)= acceptable
5-10 ɳg/ml = low, medium risk
< 5 ɳg/ml = deficient, high risk

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Malnutrition
• Levels of serum albumin
concentrations in malnourished
children
• > 3.5 g/dl = Normal
• 3-3.4 g/dl = Subnormal
• 2.5-2.9 g/dl = Low
• < 2.5 g/dl = Pathological
• Vitamin E:
• Most accepted indicator – serum
vitamin E / total lipid ratio
> 0.8 = adequate status.
• Another indicator :
Presence of hydrogen peroxide = Red
cell fragility + malonaldehyde
formation

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Vitamin K:
• Serum levels of “proteins induced by
vitamin K absence (PIVKAS)”
accumulation measured by
spectrophotometric, immunochemical,
ELISA and radio-immuno-assay
methods.
• PIVKAS are absent from normal
plasma. Their presence indicate
Vitamin K deficiency.
• In vitamin K deficiency, prothrombin
time is delayed. but less specific
indicator
• Thiamin:
Biochemical assessment are –
 urinary thiamin,
blood (serum, RBC) levels of thiamin or
its metabolite thiamin pyrophosphate
(TPP)

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• Iron:
Cut offs points for WHO definition of
Anemia
• Iodine:
Cut Off Points of Iodine (WHO)

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Calcium:
• Bone density measurements can indirectly
reflect calcium status. Radiographic and
single or dual photon absorptiometric
methods are available for measuring bone
mineral content.
Zinc:
• commonly used index = Plasma zinc
• Normal range is = 84- 104 µg/dl.
• Other indicator = leucocytes and platelets
• The normal range for leucocytes is 44.5-
361 µg/108 cells.
Riboflavin - Urinary and Blood
Niacin – the ratio of two niacin
metabolites.
• A ratio of less than 1 indicates deficiency.
• In normal subjects it ranges from 1 to 4.
Ascorbic acid:
• plasma and leucocyte ascorbic acid levels
indicate vitamin C status.
• plasma ascorbic acid (mg/dl):
> 0.3 acceptable,
0.2-0.29 medium risk
< 0.2 high risk.
• Colorimetric and HPLC techniques

10. Thank you