Biochemical Assessments Pt. 1 Flashcards
what is plasma?
the unclotted fluid minus RBC + WBC
what is serum?
any fluid left after clotting has occurred
what is sensitivity?
the ability of a test to detect a condition when it is present in a patient
high sensitivity = minimal false negative results
what is specificity?
the ability of a test to rule out the presence of a disease in someone who does not have it
high specificity = minimal false positive results
what is inter-assay variability?
the error you get when you do different measurements
what is a static assay?
measures concentration in serum/plasma
i.e. iron, zinc, retinol, folate
what can impact static assay measurements?
highly dependent on hydration status
dehydration = artificially high levels
over-hydration = artificially low levels
what is a functional assay?
measures biochemical/physiological activity
normal serum albumin level
3.5 - 5 g/dL
purpose of albumin
maintains colloidal osmotic pressure
carrier for many different substances
shortcomings for PEM assessment with albumin
- half-life of ~20 days
- large extravascular pool – can return to circulation and buffer loss
- sensitive to hydration status/edema
- sometimes infused in hospital patients
negative/positive acute phase protein: albumin
negative
transthyretin (pre-albumin) normal range
normal range: 16 - 40 mg/dL
negative/positive acute phase protein: transthyretin
negative
purpose of transthyretin
transport thyroxin and retinol-binding protein in blood
shortcomings for PEM assessment: transthyretin
- zinc deficiency can affect the synthesis
- increases with chronic renal insufficiency
- decreases with hyperthyroidism
purpose of transferrin
transport iron in bone marrow
shortcomings for PEM assessment: transferrin
- nonspecific (increases when iron stores are low)
- also increases with estrogen therapy
positive/negative acute phase protein: transferrin
negative
purpose of retinol-binding protein
binds to retinol in the blood
normal range of retinol-binding protein
3-6 mg/dL
shortcomings for PEM assessment: retinol-binding protein
- vitamin A status may complicate use
- renal patients may have elevated complications
*may be the best marker, but it is very expensive
positive/negative acute phase protein: retinol-binding protein
negative
positive/negative acute phase protein: hs C-reactive protein
positive
what is CRP good for?
could be an indicator of when to start nutrition therapy; when CRP subsides, therapy should increase
serum enzymes that indicate muscle damage
creatine kinase
lactate dehydrogenase
serum enzymes that indicate liver damage
alanine amino transferase (ALT)
aspartase amino transferase (AST)
serum enzymes that indicate pancreatic damage
amylase
lipase
normal blood glucose levels fasted + post-prandial
fasted: 70-100 mg/dL
post-prandial: <140 ~2 hours after meal
use of hA1c
indicator of average plasma glucose concentration over previous months (60-90 days)
normal hA1c levels (average adult, older adult, with DM, at risk for DM)
average adult: <5.7%
older adult: <7%
with DM: <7%
at risk for DM: 5.7-6.4%
how is bilirubin made?
break down of hemoglobin, then released in blood
what does elevated unconjugated bilirubin indicate?
elevated when liver is unable to conjugate to glucuronic acid
indicative of excessive hemolysis
what does elevated conjugated bilirubin indicate
elevated when liver is unable to excrete due to obstruction in the bile passage
what does BUN relate to?
protein intake
what does elevated BUN indicate?
decreased renal function, dehydration, GI bleeding, CHF, and high protein intake
what does low BUN indicate?
liver disease, overhydration, malnutrition, anabolic steroid use
what is creatinine?
an oxidized product of creatinine
what is creatinine used for (alongside BUN)?
a marker of renal function
normal serum sodium levels
135 - 145 mE/L
sodium is the primary intra/extracellular anion/cation?
extracellular cation
what does sodium do?
helps regulate acid-base balance, osmotic pressure, fluid distribution
normal serum potassium levels
3.5 - 5 mmol/L
potassium is the primary intra/extracellular anion/cation?
intracellular cation
causes of hypokalemia
diuretic use, vomiting, diarrhea, eating disorders, IV administration w/o K
– potentially dangerous
causes of hyperkalemia
renal failure, severe injury (burns, crushing), hypoaldosteronism, Addison’s dx
– very dangerous
causes of hypernatremia
dehydration, excessive fluid loss/output
causes of hyponatremia
excess Na loss from body – vomiting, diarrhea, suctioning, diuretics; H2O/fluid retention; SIADH
chloride is the primary intra/extracellular anion/cation?
extracellular anion
what is the purpose of chloride?
helps regulate acid-base balance, osmotic pressure, and fluid distribution
what is the purpose of potassium?
helps maintain acid-base balance, fluid balance, nerve impulse transmission
causes of hypochloremia
alkalosis and hypokalemia; bulemia
causes of hyperchloremia
kidney disease, overactive thyroid, CVD
phosphorous is correlated with
calcium
causes of hyperphosphatemia
with renal failure, hypoparathyroidism, hyperthyroidism, increased phosphorus intake, use of phosphate-containing enemas, laxatives
causes of hypophosphatemia
hyperparathyroidism, rickets, osteomalacia, chronic use of antacids containing alumni hydroxide of calcium carbonate
also with refeeding syndrome
