Biochemical Assessments Pt. 2

Question 1

three types of calcium in the body + which ones tell us what

Answer 1

1. ionized: this calcium must be measured separately from serum calcium; it tells us best about body stores
2. protein-bound: this calcium is bound to albumin; it is measured in serum calcium and is strongly associated with albumin levels
3. complexed

Question 2

causes of low calcium (hypocalcemia)

Answer 2

hypoparathyroidism (PTH releases calcium from stores)
severely low vit D stores (vit D helps release calcium from stores)
renal dx
acute pancreatitis

Question 3

causes of high calcium (hypercalcemia)

Answer 3

hyperparathyroidism (PTH releases calcium from stores)
vitamin D toxicity (vit D helps release calcium from stores)
hyperthyroidism

Question 4

what is albumin-corrected total calcium?

Answer 4

allows you to see calcium levels independent of albumin status
you need: normal albumin, pts albumin, and pts serum calcium

Question 5

what is anemia?

Answer 5

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

Question 6

four types of anemia

Answer 6

microcytic
macrocytic
normocytic
pseudo

Question 7

causes of microcytic anemia

Answer 7

Fe deficiency
thalassemia (inherited disorder where body doesn’t make enough hemoglobin)
chronic disease
lead poisoning

Question 8

causes of macrocytic anemia

Answer 8

B12 deficiency
folate deficiency

Question 9

causes of normocytic anemia

Answer 9

blood loss
chronic disease

Question 10

causes of psuedo anemia

Answer 10

increased fluid in body
pregnancy
endurance training

Question 11

what does MCV tell us?

Answer 11

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)

Question 12

what does RDW tell us?

Answer 12

red blood cell distribution width
the standard deviation of blood cell size (>15% tells you there are two different types of anemia occurring)

Question 13

causes of B12 deficiency

Answer 13

typically due to intrinsic factor problems
intrinsic factor is needed for the absorption of all B12

Question 14

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)

Answer 14

serum iron: decrease
ferritin: decreases
TIBC: increases
transferrin saturation: decreases
free transferrin: increases
ZPP or EPP: increases
sTfR (soluble serum transferrin receptor): increases

Question 15

what is the best way to determine iron status?

Answer 15

using models
one marker is typically not enough to determine problems and diagnosis

Question 16

what happens to ferritin under stress?

Answer 16

acute phase protein – will increase
this can sometimes mask low iron stores

Question 17

three stages of iron depletion

Answer 17

tissue depletion – function has not decreased yet
functional deficiency without anemia – functions begin to falter
microcytic anemia

Question 18

measures of B12

Answer 18

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

Question 19

measures of zinc

Answer 19

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

Question 20

what can cause serum Zn to decrease?

Answer 20

stress, inflammation, infection, estrogen use, corticosteroid use, after meals (increases with fasting)

Question 21

measures of magnesium

Answer 21

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

Question 22

Mg and __ are tightly linked; deficiency of one affects other

Answer 22

calcium

Question 23

measures of iodine

Answer 23

24-hour urinary iodine: most widely used indicator of recent iodine intake and nutritional status

spot urine: can help you determine population levels

Question 24

measures of potassium

Answer 24

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

Question 25

measures of phosphorous

Answer 25

no real marker of phosphorous status

serum phosphorus can be increased with intake or renal patients

Question 26

measures of calcium

Answer 26

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

Question 27

measures of selenium

Answer 27

no gold standard biochemical marker

serum selenium: not reflective

plasma glutathione peroxidase: can be used but not very good

Question 28

measures of vit A

Answer 28

serum retinol: best indicator (sensitive on both high and low ends, but not in the normal)

best to do RBP and serum together

Question 29

retinol-binding protein can be influenced by

Answer 29

malnutrition and inflammation
so if these are present, the test might not be as reflective or accurate

Question 30

what vit B deficiencies are expected together?

Answer 30

thiamine + niacin + riboflavin + B6

B12 + iron + zinc

folate + vitamin C

Question 31

why is thiamine supplementation needed in alcoholics?

Answer 31

thiamine absorption is significantly decrease
so status of thiamine will be decreased
other deficiencies will be present, but this is the biggest

Question 32

measures of thiamine (B1)

Answer 32

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

Question 33

what will a carbohydrate diet do to thiamine needs?

Answer 33

increase

thiamine is needed heavily in the carbohydrate metabolism pathways

Question 34

measures of riboflavin (B2)

Answer 34

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

Question 35

measures of niacin (B3)

Answer 35

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

Question 36

measures of B6

Answer 36

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

Question 37

measures of folate

Answer 37

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

Question 38

measures of vit B12 (cobalamin)

Answer 38

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)