interpretation of clinical lab tests

Question 1

sensitivity

Answer 1

if neg can be certain it is neg
may give false positive
screening

Question 2

specficity

Answer 2

if pos can be certain it is pos

confirm diagnosis

Question 3

incidence

Answer 3

number of new cases of a disease or condition in a specified time period divided by size of population who were initially disease free
direct measure of risk

Question 4

prevalence

Answer 4

actual number of cases alive w/disease during a period of time or at a specific date

Question 5

what LDs are in the heart

Answer 5

LD1 (60%)

LD2 (30%)

Question 6

LDH and MI

Answer 6

rise w/in 24-48 hrs after MI
peaks in 2-3 days
returns to normal in 5-10 days
S&S >90% when elevated >40% w/in 24hours

Question 7

CPK and MI

Answer 7

S&S >90% w/in 7-18 hours
peak concentration w/in 24 hours
returns to normal w/in 2-3 days

Question 8

very high CPK

Answer 8

poor sensitivity

Question 9

very low CPK

Answer 9

poor specificity

Question 10

CPK relative index

Answer 10

measure of mass of CPK-MB fraction/total CPK x100
used if total CPK is elevated
ratio 5 indicative of cardiac

Question 11

myoglobin

Answer 11

elevated w/in 2-4hrs
peak at 6-12
normal 24-36
not very sensitive

Question 12

troponin

Answer 12

rise 3-12 hrs
peak 24-48
normal 5-14 days

Question 13

cardiac specific troponins

Answer 13

cTnI

cTnT

Question 14

lab tests for anemia

Answer 14

reticulocyte count
bilirubin
coombs test
BUN, creatinine
bone marrow aspiration 
occult blood
UA
lead
osmotic fragility testing

Question 15

hypochromic

Answer 15

less hemoglobin in cell

enlarged area of central pallor

Question 16

spherocyte

Answer 16

loss of central pallor
stains more densly
often microcytic

Question 17

target cell

Answer 17

hypochromic w/central target of hemoglobin
liver disease
thalessemia
hemoglobin D
postsplenectomy

Question 18

leptocyte

Answer 18

hypochromic cell w/normal diameter and decreased MCV

thalassemia

Question 19

elliptocyte

Answer 19

oval cigar shaped
hereditary
certain annemias

Question 20

schistocyte

Answer 20

fragmented helmet or triangular shaped
microangiopatic anemia
artificial heart valves
uremia
malignant HTN

Question 21

stomatocyte

Answer 21

slitlike area of central pallor in erythrocyte

liver disease, acute alcoholism cancer, hereditary, artifact

Question 22

tear-shaped RBCs

Answer 22

drop shaped
often microcytic
myelofibrosis
thalassemia

Question 23

acanthocyte

Answer 23

5-10 spicules unevenly distributed and varying lengths

Question 24

echinocyte

Answer 24

evenly distributed spicules, 10-30
uremia
peptic ulcer
gastric cancer
pyruvic kinase deficiency
artifact

Question 25

oliguria

Answer 25

<500ml in 24 hours

Question 26

prerenal failure

Answer 26

a few hyaline casts
fine granular casts
little proteins, heme, or red cells
SG increased

Question 27

intrinsic renal

Answer 27

hematuria, proteinuria are prominent
brown granular cass
red cell casts- acute glomerulonephritis
white cell casts- acute interstitial neprihitis

Question 28

pre renal values

Answer 28

SP >120
urinary to plasma creatinine >40
urinary to plasma osmolality >1.5
urinary Na concentration is <15

Question 29

renal failure values

Answer 29

urinary to plasma creatinine 40

FENa >2%

Question 30

BUN:creatinine

Answer 30

pre renal >20:1

renal <20:1

Question 31

reduction of pH by .1

Answer 31

raises serum K by .3