NA part 2 Flashcards
What is biochemical assessment and why is it important?
Measurement of nutritional markers in blood, urine (and other fluids and tissues)
• Detects subclinical nutrient deficiencies- nutritional deficiencies that are not yet severe and don’t show physical symptoms
What do biochemical assessment examine?
- Visceral and somatic proteins
- Hematological assessment
- Lipid profile
- Micronutrient assessment
- Immunocompetence assessment mainly through lymphocyte count
What are biochemical markers affected by?
- Nutritional status, medication, illness/physiological state
What is visceral protein status reflected by? Why do we need to sample it
serum proteins, RBC, WBC
we cannot do a biopsy of vital organs to test the status of vital proteins, but we can test serum proteins
Malnutrition causes decrease in oran mass and substrate supply and thus inflicts a decrease a decrease in the synthesis of serum proteins
What are the components of the blood
- Albumin- most abundant
- Fibronectin
- Transferrin (includes prealbumin aka transthyretin (thryoid hormone transport) and retinal-binding proteins
Are serum proteins are good markers of malnutrition?
No They are indeed affected by malnutrition and thus can serve as markers of it but-> Low sensitivity and specificity for nutritional status; influenced by: - Poor protein intake - Altered metabolism and synthesis - Hydration - Inflammation - Pregnancy - Medications - Exercise
How does inflammation affect serum proteins?
Decreases the level of serum proteins
What are the lives of various serum proteins
- Albumin (most abundant) - T 1⁄2 17-21 days
- Transferrin- T 1⁄2 8-10 days
- Prealbumin or transthyretin (TTR) - T 1⁄2 2-3 days
- Retinol Binding Protein (RBP) - T 1⁄2 10-12 hours
Why would we need to know half-lives of serum proteins? What are the ways of overcoming the problems we encounter?
important to know half-lives when we implement treatment to see if we are improving when on treatment
sometimes the change is not reflected during re-assesment as albumin doesn’t have time to be replaced as it has along half life.
this however can be overcome by measuring prealbumin
Function of albumin
Maintains osmotic pressure
Transport of large insoluble molecules, drugs, calcium, zinc
Function of transferrin
Iron transport
Function of TTR
Transport of T3 and T4
Carrier for RBP (retinol binding protein)
Function of RBP
Retinol transport from liver to periphery Circulates with TTR
When is albumin high and low
High- during dehydration
Low- during low protein intake, malabsorption, trauma, surgery, overhydration, edema, acute illness, aging, inflammation
When is transferrin high; low
High- during Fe deficiency, pregnancy, chronic loss
Low- during acute illness, chronic infection, PEM, systemic disease
When is TTR high; low
High- during renal disease, Hodgkins disease (blood cancer that starts in the lymphatic system)
Low- during Liver disease, PEM, chronic loss, malabsorption, hyperthyroidism
When is RBP high; low
High- during renal disease
Low- during Vitamin A deficiency, zinc deficiency, hyperthyroidism, liver disease
What is the connection between cytokines and acute phase proteins?
cytokines stimulate liver to make acute phase proteins
Name negative acute phase proteins
How are they affected by inflammation, illness or metabolic stress?
Albumin, transferrin, TTR and RBP are negative acute- phase proteins: levels decrease by >25% during inflammation, illness or metabolic stress
Describe C-reactive protein (CRP)?
What is used to asses?
What are the normal levels
C-reactive protein (CRP) is a positive acute-phase protein
– Used to detect mild or acute inflammation –> Normal <1, mild chronic 1-5, acute >5 mg/L
– Not a nutritional marker but very useful to interpret other serum proteins
CRP is also a marker of CVD
Which organ makes C-reactive protein?
liver
What are the cutoff for albumin?
Normal level is above 35g/L
Name ways to assess somatic protein status
Nitrogen balance
Creatine excretion
Immune function
What does nitrogen balance assess?
- Reflects total protein retention or losses (but not mass)