Principles of Lab testing Flashcards Preview

Block 6 > Principles of Lab testing > Flashcards

Flashcards in Principles of Lab testing Deck (31):
1

highest source of error

preanalytic- wrong tube, wrong patient

2

phases of testing

pre analytic
analytic
post analytic

3

source of error in analytic phase

imprecise instrument

4

source of error post analytic phase

results don't make sense in clinical context

5

precision

consistent, repeatable results (cluster on target)

6

measures of central tendency

mean
median

7

measures of variability

standard deviation
coefficient of variation

8

meaning of coefficient of variation

low = precise

9

accuracy

closest to true value (near bullseye)

10

sensitivity

probability of a positive test given a disease
a/a+c

11

use of sensitivity

rule out a diagnosis- screening

12

specificity

probability of negative test given no disease
d/b+d

13

use of specificity

confirm a diagnosis

14

what changes with prevalence

PPV and NPV

15

what is constant

sensitivity and specificity

16

which s better for individual patients

PPV and NPV

17

prevalence

probability of having the disease (pretest probability)

18

PPV

probability of disease given positive result
a/a+b

19

NPV

probability of no disease given negative result
d/c+d

20

Bayes's therom

P(D+|T+) = P(T+|D+) * P(D+)/P(T+)

21

truth table set up

top- Disease + disease -; a to b
side- test + test -; c to d

22

types of bias

availability
representativeness
anchoring
value-induced

23

availability

overestimation based on recent experience

24

representativeness

overestimation of rare disease based on typical picture

25

anchoring

failure to change theory based on new information

26

value-induced

overestimate based on association with bad outcomes

27

source of reference interval

95% confidence interval

28

determination of cut off values

trade off between sensitivity and specificity- use ROC curves

29

ROC curve

sensitivity vs 1-specificity
best with greatest AUC has greater discriminatory vale

30

LR+

sensitivity / 1-specificity

31

LR-

1-sensitivity / specificity