Transcript Laboratory Values for Nutritional Assessment

Midterm Exam
Thursday, May 3, 3PM
or by arrangement
pick up labs on Tuesday at 2PM in 129 MI

Topics:




Closed book (< 20 minutes)



Theory and principles
Lecture and sections of text that support lecture materials
Open book/notes/lab reports/calculators (~30 minutes)




Intro to Nutrition Assessment
Anthropometric Assessment
Body Composition Assessment
Be able to do all calculations/assessments you did for labs
Know how before coming to class
Total test time = 50 minutes
May 8 & 10


Glucose tolerance test
Fast 6-8 hours before class (no caloric foods after 8AM)
Laboratory Values
for Nutritional
Assessment
David L. Gee, PhD
FCSN 442
Nutrition Assessment Laboratory
Biochemical Assessment of
Nutritional Status

Compared to anthropometric, clinical
methods, and dietary intake data,
biochemical assessment is



Most objective and precise
More sensitive
However, can be misinterpreted or affected
by factors unrelated to stated assessment
Uses of Biochemical Measures

Static Tests (direct tests)

Measurement of a nutrient or metabolite




Blood glucose concentration
Blood folic acid concentration
Blood calcium concentration
May fail to reflect overall nutritional status

Blood calcium normal in patients with
osteoporosis
Uses of Biochemical Measures

Functional Tests (indirect tests)



Assesses nutritional status by looking at a
function of that nutrient
Glucose tolerance test for glucose
intolerance
Histidine load test (FIGLU) for folate status

HIS
FIGLU
GLU
Uses of Biochemical Measures

Validate dietary assessment

Protein intake


24-hour urinary nitrogen excretion
Energy intake




Doubly labeled water method
Drink 2H2O + H218O
2H O only lost from body as water
2
H218O lost from body as water or C18O2




CO2 + H2O <-> H2CO3
Collect urine periodically over 3 weeks and measure
difference of 2H2O and H218O
Greater the difference, the greater the metabolic rate.
Milk intake

Plasma levels of C15:0 fatty acids
Understanding lab values

Understanding the metabolic basis of
the laboratory test

Biological sample used



Blood, plasma, serum
Urine
Factors affecting the concentration of the
metabolite measured
Example: nitrogen metabolism

Amino acid metabolism

Urea synthesis in liver



From ammonia and aspartic acid
Urea excretion in kidneys
Questions?



What are causes of elevated BUN? (uremia)
What are factors that cause urinary urea nitrogen
to go up?
What are causes of elevated blood ammonia
(hyperammonemia)
Assessment of Renal
Function:
Blood Urea Nitrogen


BUN
Urea: end product of amino acid metabolism




Produced in liver
 Site of urea cycle
Excreted by kidneys
Elevated due to renal insufficiency
Injured liver results in elevated ammonia
concentrations
Other factors affecting [BUN]

Dehydration


Severe liver disease


Decreases BUN
High dietary protein intake



Decreases BUN
No effect
24-hour Urinary urea excretion affected by
protein intake
Hemodialysis patients

Increases between dialysis
Lab Values for Creatinine
-Blood creatinine concentration
-Urinary creatinine concentration
Serum Creatinine



Endproduct of creatine metabolism
Excreted by kidneys into urine
Blood creatinine concentration

Increases in blood creatinine


Renal insufficiency
Urinary excretion (24hr)

proportional to total muscle creatine


Proportional to muscle mass
Also affected by


meat consumption
creatine supplementation
Bilirubin






Endproduct of heme catabolism
Made in spleen, liver, bone marrow
Conjugated with glucuronic acid in
liver
Excreted into bile from liver
Elevated bilirubin is neurotoxic
Jaundice

Conjugated bilirubin



Glucuronic acid
Conjugation occurs in liver to enhance
water solubility
“direct bilirubin
Newborn Jaundice
Bilirubin

Indirect Bilirubin




free bilirubin (unbound)
circulating form
Production of bilirubin from hemoglobin
occurs in spleen, liver, and bone marrow
Direct Bilirubin



bilirubin conjugated (bound) to other
compounds (glucuronic acid)
made in liver
excreted in bile
Elevated Direct Bilirubin
Post hepatic jaundice
 Causes by

obstruction in liver
 obstruction in bile duct

Elevated Indirect Bilirubin

Pre-hepatic jaundice

Causes:
excessive hemolysis
 liver disease



hepatitis
premature infants

underdeveloped liver