Biochemical Assessments Pt. 2 Flashcards
three types of calcium in the body + which ones tell us what
- ionized: this calcium must be measured separately from serum calcium; it tells us best about body stores
- protein-bound: this calcium is bound to albumin; it is measured in serum calcium and is strongly associated with albumin levels
- complexed
causes of low calcium (hypocalcemia)
hypoparathyroidism (PTH releases calcium from stores)
severely low vit D stores (vit D helps release calcium from stores)
renal dx
acute pancreatitis
causes of high calcium (hypercalcemia)
hyperparathyroidism (PTH releases calcium from stores)
vitamin D toxicity (vit D helps release calcium from stores)
hyperthyroidism
what is albumin-corrected total calcium?
allows you to see calcium levels independent of albumin status
you need: normal albumin, pts albumin, and pts serum calcium
what is anemia?
condition characterized by a reduction in the number of erythrocytes per unit of blood volume, or a decrease in hemoglobin content of blood below the concentration of physiologic need
four types of anemia
microcytic
macrocytic
normocytic
pseudo
causes of microcytic anemia
Fe deficiency
thalassemia (inherited disorder where body doesn’t make enough hemoglobin)
chronic disease
lead poisoning
causes of macrocytic anemia
B12 deficiency
folate deficiency
causes of normocytic anemia
blood loss
chronic disease
causes of psuedo anemia
increased fluid in body
pregnancy
endurance training
what does MCV tell us?
mean cell volume
tells us if it’s microcytic (small cells due to improper hemoglobin development) or macrocytic (large cells due to lack of organelle breakdown)
what does RDW tell us?
red blood cell distribution width
the standard deviation of blood cell size (>15% tells you there are two different types of anemia occurring)
causes of B12 deficiency
typically due to intrinsic factor problems
intrinsic factor is needed for the absorption of all B12
what occurs to each of these labs with iron deficient anemia
serum iron
ferritin
TIBC
transferrin saturation
free transferrin
ZPP or EPP
sTfR (soluble serum transferrin receptor)
serum iron: decrease
ferritin: decreases
TIBC: increases
transferrin saturation: decreases
free transferrin: increases
ZPP or EPP: increases
sTfR (soluble serum transferrin receptor): increases
what is the best way to determine iron status?
using models
one marker is typically not enough to determine problems and diagnosis
what happens to ferritin under stress?
acute phase protein – will increase
this can sometimes mask low iron stores
three stages of iron depletion
tissue depletion – function has not decreased yet
functional deficiency without anemia – functions begin to falter
microcytic anemia
measures of B12
serum holo-transcobalamin: will decrease with deficiency; the best marker, but it is expensive
urinary or serum methylmalonic acid (MMA): will increase with deficiency
total homocysteine: will increase with deficiency; not specific
measures of zinc
serum Zn: a good marker of deficiency but not sensitive to low/high normal
(serum Zn is maintained at the expense of tissue Zn)
24-hour urine Zn: a much better measure, but rarely done
what can cause serum Zn to decrease?
stress, inflammation, infection, estrogen use, corticosteroid use, after meals (increases with fasting)
measures of magnesium
serum Mg: the common lab test done – but it does not reflect tissue stores well
it will show when a deficiency occurs
Mn loading test: the gold standard, but rarely done
Mg and __ are tightly linked; deficiency of one affects other
calcium
measures of iodine
24-hour urinary iodine: most widely used indicator of recent iodine intake and nutritional status
spot urine: can help you determine population levels
measures of potassium
serum potassium: not a good marker of intake status; may be low with excessive diarrhea and vomiting
24-hour urinary potassium: best marker of intake
second morning void can also be reflective of status
measures of phosphorous
no real marker of phosphorous status
serum phosphorus can be increased with intake or renal patients
measures of calcium
no appropriate measure of calcium status
serum calcium: a very poor indicator – doesn’t show in the case of deficiency because PTH regulates it so tightly
24-hour urinary calcium: somewhat reflective of changes in dietary calcium
measures of selenium
no gold standard biochemical marker
serum selenium: not reflective
plasma glutathione peroxidase: can be used but not very good
measures of vit A
serum retinol: best indicator (sensitive on both high and low ends, but not in the normal)
best to do RBP and serum together
retinol-binding protein can be influenced by
malnutrition and inflammation
so if these are present, the test might not be as reflective or accurate
what vit B deficiencies are expected together?
thiamine + niacin + riboflavin + B6
B12 + iron + zinc
folate + vitamin C
why is thiamine supplementation needed in alcoholics?
thiamine absorption is significantly decrease
so status of thiamine will be decreased
other deficiencies will be present, but this is the biggest
measures of thiamine (B1)
erythrocyte transketolase activity coefficient (used by running the blood w/ and w/o thiamine to see the substrate activity): this is the best indicator
urinary thiamine: may be more reflective of recent dietary intake than true status
if we suspect thiamine though, deficiency will probably be run without testing
what will a carbohydrate diet do to thiamine needs?
increase
thiamine is needed heavily in the carbohydrate metabolism pathways
measures of riboflavin (B2)
erythrocyte glutathione reductase activity coefficient (ECRAC) (used by running the blood w/ and w/o riboflavin to see the substrate activity): a good marker, but expensive
measures of niacin (B3)
no functional assessment markers
some urinary end products can be used as indicators: N’methylnicotinamide (NMN), N’methyl-2-pyridone-5-carboxylamide (2-pyridone)
if you measure both urinary products and they are both low, this is a gold standard that niacin is low
measures of B6
fasting plasma PLP: the single best indicator for healthy persons; but it isn’t a great indicator; impacted by a lot of things– protein intake decreases it, physical activity increases it, age decreases, it, blood glucose decreases it
measures of folate
erythrocyte folate concentration (reflective of liver stores and total body status): considered best clinical index
serum folate concentration: index of recent folate intake
serum and erythrocyte folate
measures of vit B12 (cobalamin)
no gold standard but some of the tests include …
serum/plasma total cobalamin
serum holo-transcobalamin
total homocystine (tHcy)
urinary or serum methylmalonic acid (MMA)
