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PCM II Exam 1 > Diagnosis by Lab Methods > Flashcards

Diagnosis by Lab Methods Flashcards

1
Q

sensitivity

A

rate of true positive of test

very sensitive - always positive for someone who has disease

good negative predictive value

if positive - can’t conclude they have disease

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2
Q

specificity

A

good positive predictive vale

positive specific test - 100% certain have disease

negative - doesn’t mean they don’t have disease

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3
Q

tests with high specificity

A

used to CONFIRM results of sensitive, but less specific screening test

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4
Q

incidence

A

number of new cases of disease in specified period

divided by size of population under consideration who were initially disease free

measure of RATE

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5
Q

prevalence

A

actual number of cases during period of time or at particular date in time

measure of COMMONALITY

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6
Q

chronic incurable disease

A

low incidence but high prevalence

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7
Q

highly contagious, rapidly fatal disease

A

high incidence, but low prevalence

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8
Q

work up in chest pain labs

A
  • serum lactate DH
  • serum creatinine phosphokinase
  • serum myoglobin
  • serum troponin
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9
Q

1975

A

galen first use if CPK, LD, and isoenzymes

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10
Q

1985

A

CK MB

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11
Q

1991-1992

A

troponins

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12
Q

lactate DH

A

LDH
-enzyme catalyzes coversion of lactate to pyruvate

cells die - release LDH to blood

seen in many different cells

not good predictive value

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13
Q

good thing about LDH

A

stays high in serum for long time

useful in someone with bad chest pain 36 hours ago
-may still be elevated

hemolysis also causes elevation of LDH-1
-NOT THAT SPECIFIC

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14
Q

CPK

A

catalyzes reversible transfer of P between creatinine and phosphocreatine as well as between ATP and ADP

BB - brain
MB - cardiac
MM - skeletal m

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15
Q

sensivitiy/specificity of CPK-MB

A

> 90%

within 7-18 hours

quicker and more specific

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16
Q

CPK relative index

A

mass of CPK-MB fraction / total CPK x 100

ratio less than 3 - skeletal m source

ration grater than 5 - cardiac source

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17
Q

myoglobin

A

O2 binding in muscle tissue

sensitive test - but not enough

levels rise early after muscle damage

elevated 2-4 hours after symptoms, peak 6-12 hours, normal 24-36 hours

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18
Q

temporal changes in CK-MB and myoglobin

A

myoglobin rapid increase

CK - MB - less rapid increase

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19
Q

troponin

A

regulatory protein in striated muscle

calcium channels open - Ca causes troponin to change shape allowing actin and myosin to bind leading to contraction

three subunits
-TnC - binds Ca
TnT - binds tropomyosin
TnI - binds actin

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20
Q

troponin levels

A

gold standard for determining myocardium damage

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21
Q

serum troponin levels

A

increase 3-12 hours after onset of chest pain, peak 24-48 hours, return to baseline 5-14 days

criterion standard*** for diagnosing myocardial infarction

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22
Q

troponin C

A

same all muscle tissue

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23
Q

troponin I and T

A

cardiac specific

-these ones used

24
Q

78yo F - weak and dizzy, HTN, lethargic, mucous membrane pale, murmur, lungs CTA

A

anemic

25
Q

work up for anemia

A

blood loss - most common

marrow - decreased production
hemolysis - destruction

iron deficiency - most common etiology

26
Q

most common cause of anemia

A

blood loss

27
Q

lab tests for anemia

A 
RBC count
peripheral smear
serum iron
total iron binding
serum ferritin
retic count
RBC distribution
28
Q

elevated bilirubin

A

hemolysis

29
Q

CBC

A

give you indices

  • MCV
  • MCHC
  • chronic iron deficiency anemia - both below normal range

after blood loss - cellular indices do not enter abnormal range until after most erythrocytes destroyed (120 days)

30
Q

anemia

A

ranked basis of size and Hg content

microcytic hyperchromic
-and others

**know this

31
Q

microcytic hypochromic erythrocytes on peripheral smear

A

chronic iron deficiency anemia

32
Q

folate and iron deficiency

A

common in areas of world with little fresh meat and produce

peripheral smear - population of macrocytes** mixed among microcytic hypochromic cells

can normalize the MCV

33
Q

sickle cell anemia

A

see on peripheral smear

not rounded and concave

  • RBCs misshaped
  • looked like sickles

doesn’t hold O2

34
Q

Dx of iron deficiency

A
  • low serum iron and ferritin
  • elevated TIBC

normal serum ferritin - deficienct in iron with coexistent diseases

hepatitis or anemia of chronic disorders

35
Q

red blood cell indices

A

do not become abnormal for several moths after tissue stores are depleted of iron

36
Q

hemoglobin studies

A

Hg A2 and fetal Hg

  • electrophoresis - measure of Hg A2 and fetal Hg
  • useful for establishing beta-thalassemia or Hg C or D as etiology of microcytic anemia
37
Q

reticulocyte Hg content

A

and serum iron are only parameters independently associated with iron deficient anemia

38
Q

stool testing

A

Hg in stool - GI bleed

very common etiology for anemia

39
Q

absence of stainable iron in bone marrow aspirate**

A

permits establishment of diagnosis of iron deficiency without other lab tests

40
Q

61yo M - ICU, repair of ruptured aneurysm, lost blood, transfused, urine output has been slowing

A

oliguria

41
Q

oliguria

A

diminished capacity to form and pass urine less than 500mL in 24 hours

imbalance of body fluids / electrolytes

renal disease

urinary tract obstruction

42
Q

prerenal failure

A

hyaline and fine, granular casts observed on urinalysis

increased specific gravity

43
Q

renal failure

A

hematuria and proteinuria are prominent

-brown granular casts are typically found in ischemic or toxic acute tubular necrosis

44
Q

acute interstitial nephritis

A

white cells in urinalysis

eosinos and white cell casts

45
Q

postrenal

A

obstruction

46
Q

prerenal

A

high specific gravity
high urine:plasma Cr
low urine sodium
low FENa

hypovolemia**

47
Q

renal

A

urine:plasma Cr
osmolality ratio 40
FENa >2

intrinsic renal disease**

48
Q

BUN/Cr

A

> 20:1 prerenal
<20:1 renal failure

Cr - varies with age

lose 50% of kidney function - may not have change in serum Cr

49
Q

serum Na

A

useful in diagnosis cause of oliguria

50
Q

hyponatremia

A

fluid retention, administration of hypotonic fluid

51
Q

hypernatremia

A

secondary to dehydration

52
Q

serum K

A

oliguria - decreased GFR - reduced tubular secretion - metabolic acidosis - increased serum potassium

53
Q

0.1 reduction in arterial pH

A

raises serum potassium by 0.3

54
Q

reasons for ordering lab test

A

diagnosis**
monitor
screen
research

55
Q

shotgun-ordering

A

large number of lab tests that may or may not have adequate diagnostic predictive value in identifying particular disease

56
Q

rifle-ordering**

A

specific lab tests based on assessment of their diagnostic accuracy and predictive value in identifying a particular disease

57
Q

how will test results influence patient management?

A

important question before ordering a lab test

PCM II Exam 1 (6 decks)

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