Biochemical (Laboratory Assessment of Nutritional Status) Flashcards
What is the advantage of biochemical tests? Disadvantage?
Advantage: Objective and quantitative; Disadvantage: No specific lab test that can diagnose malnutrition need to look at multiple test in addition to other components of the nutrition assessment process
What are the purposes of Laboratory tests?
1) Diagnose a disease 2) Evaluate treatment plans 3) Monitor effectiveness of medications
What are the routine medical tests?
CUCS: Clinical Chemistry Panels, Urinalysis, Complete blood count, Stool Testing
Clinical Chemistry Panels
Blood work
Urinalysis
Metabolic and kidney disorders, infection
Complete blood count
count of the cells of the blood and description of RBCs
Stool test
presence of blood, pathogens, and gut flora
Reference Ranges
Constructed from a large number of test values (20 ->1000), reflect values found in approx 95% of population; 2.5% will fall above, 2.5% will fall below; 1/20 will have values outside of reference ranges.
Critical Difference
The change in a lab value that is significant enough to give evidence that their is a problem. It is also important to understand trends
What are the two routes that lead to malnutrition?
Starvation or stress/disease/injury
Malnutrition: Starvation
1) Low food resources 2) Chronic starvation by choice 3) Anorexia nervosa
Chronic-Disease-Related Malnutrition
1) Liver Failure 2) Kidney Failure, Cancer
Acute Disease or Injury related malnutrition
Major infection, Burns, trauma, traumatic brain injury
How does acute inflammation effect body composition?
Lean body mass is used to synthesize cytokines, positive acute-phase proteins, lactic acid, and white blood cells. Protein synthesis of other body parts is halted.
How do cytokines effect systemic processes?
Cytokines increase the breakdown of muscle protein, alter the synthesis of albumin and pre-albumin by the liver, and overall stimulate and inhibit bodily functions.
Negative Acute phase respondents
Decrease in response to acute phase proteins: albumin; pre-albumin (transthyretin); retinol binding protein; transferrin
Positive Acute phase respondents
increase in response to acute-phase:
CRP. Increase often proportional to severity of tissue damage.
When do APP levels fluctuate?
in response to tissue injury; trauma, burns, acute infections, M.I etc.
What is the best marker for the inflammatory process?
CRP C-reactive protein: when levels decrease, patient is entering a stage of anabolism; nutrition becomes more and more important here.
What is the disadvantage of CRP testing?
It is expensive, you need multiple measurements.
Vital signs of inflammation:
Increased Temperature, heart rate, respiratory rate, blood pressure
Laboratory signs of inflammation
Elevated WBC, CRP, glucose, depleted albumin.
Anthropometric signs of inflammatory process.
Unintended weight-loss, loss of muscle mass, protein-energy metabolism
What protein assessment is used most commonly?
Nitrogen balance. Tells us the presence and severity of a catabolic state. Others include creatine and albumin tests.
Creatine levels
Fairly constant; proportional to muscle mass.
What is the major by-product of protein metabolism?
Urea; excretion 12-20 g/day
What are some of the limitations to the nitrogen balance test?
1) Hard to collect a valid specimen 2) Accuracy of assessing protein intake 3) Positive balance does not mean catabolism has decreased
What is the most abundant protein in plasma?
Albumin 60%; half life 18-21 days
What is the major function of albumin?
Maintain colloidal osmotic pressure (keeping fluid within’ circulation)
What factors influence the levels of albumin in the plasma?
1) Increases with dehydration; decreases with over-hydration 2)Influenced by acute stress and inflammatory response (inversely related) 3) Influenced by underlying conditions.
Albumin in the elderly
1) depressed levels common 2) low levels not accountable by (diet and weight) are attributed to chronic inflammatory response. 3) Need to treat the underlying causes of albumin levels
What is the critical difference value for albumin?
8%
