Assessment of Nutritional Status - Biochemical

Question 1

What are the two kinds of biochemical test?

Answer 1

static

functional

Question 2

Describe static tests

Answer 2

Measure of nutrient or metabolite in biological sample e.g.,

• blood
• urine
• serum
• faeces

Question 3

What is a limitation of static testing?

Answer 3

fail to reflect the overall nutritional status of an individual
e.g.,
blood test may show low Ca level in blood but this does not indicate poor bone health overall

Question 4

describe functional tests

Answer 4

assessing performance of one or more physiologic functions that rely on a specific nutrient for optimal performance

Question 5

give an example of a functional test

Answer 5

dark adaptation test for vit A deficiency

Question 6

What is a limitation of functional tests?

Answer 6

non specific - can identify that there may be a nutrient deficiency but can’t specify which nutrient

Question 7

list some confounding factors (subject related, method related, sample related and health related) that may influence the result of a biochemical test

Answer 7

• subject related factors e.g., age, sex, ethnicity, weight, diet
• method related factors e.g., precision, accuracy, validity, sensitivity
• sample factors e.g., contamination or haemolysis
• health related factors e.g., disease

Question 8

what is the difference between test sensitivity and test specificity

Answer 8

test sensitivity
- ability of a test to identify who does have the deficiency

test specificity
- ability of a test to identify who does not have the deficiency

Question 9

What is positive predictive value?

Answer 9

probability of those with positive result truly have the deficiency

Question 10

what is negative predictive value?

Answer 10

probability that those who receive a negative result truly don’t have the disease

Question 11

what are the four stages in the analysis of biopsy material?

Answer 11

sample
storage
prep
analysis

Question 12

What information can you yield from measuring nutritional biomarkers in biological tissues e.g., blood, urine, muscle?

Answer 12

• can compare nutrient intake with estimated intake from dietary assessment
• validates dietary assessment
• detect pre-clinical disease
• test subject exposure to dietary interventions

Question 13

what are some factors that can influence blood?

Answer 13

hydration 
fasting/eating
medications
infection
inflammation

Question 14

Why is blood a favourable biological sample?

Answer 14

easy to obtain
non-invasive
easy to analyse

Question 15

why do plasma and serum nutrient levels reflect recent dietary intake?

Answer 15

plasma and serum carry recently absorbed nutrients to body tissues

Question 16

why would you conduct a fasting blood test?

Answer 16

when you want to look at long-term/chronic deficiency

plasma and serum levels reflect recently absorbed nutrients therefore fasting reduced serum/plasma nutrient levels

Question 17

what is the difference between serum and plasma?

Answer 17

serum = plasma without the clotting factors (fibrin)

plasma = component of blood in which blood cells are suspended along with proteins and clotting factors

Question 18

what does the nutrient content of erythrocytes show and why?

Answer 18

chronic nutrient deficiency

lifespan of these cells is long (120 days)

Question 19

what are the 3 types or urine test?

Answer 19

• fasting
• 24 hour
• 2nd fasted early morning

Question 20

Why is urine testing favourable?

Answer 20

cheap

non invasive

Question 21

does urine content reflect acute or chronic nutritional status?

Answer 21

acute

Question 22

describe a limitation of urinary testing

Answer 22

certain factors e.g., infection, antibiotics, alcoholism can increase nutrient levels in urine so may not accurately reflect nutrient status

Question 23

list the 6 main serum proteins

Answer 23

serum albumin
serum pre-albumin 
thyroxine binding pre-albumin 
transferrin
retinol binding protein
insulin-like growth factor 1 (IGF-1)

Question 24

Describe Nitrogen-balance as a method of assessing protein status

Answer 24

measurement of nitrogen excretion to monitor changes in total protein mass

Question 25

what is the equation for nitrogen balance?

how is nitrogen intake calculated?
how is nitrogen loss calculated?

Answer 25

nitrogen balance = nitrogen intake - nitrogen loss

nitrogen intake = protein intake (g) / 6.25
nitrogen loss = urinary urea nitrogen + 4

Question 26

list some indicators of total body protein status

Answer 26

mid arm muscle circumference
total body potassium level
total body nitrogen level
densitometry

Question 27

Why is immunocompetence used as a measure of nutritional status?

Answer 27

there is a close relationship between immunity and nutritional status

immunocompetence = early indicator of nutrient deficiency