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PATHOLOGY > Using Laboratory Data > Flashcards

Flashcards in Using Laboratory Data Deck (52):
1

Reasons to order lab test

Diagnosis:confirm, screen, rule-out
Management: monitor, follow course, prognosis
Fear: criticism, insecurity

2

Most common reasons for ordering a lab test?

diagnosis, screening, monitoring

3

Lab test most likely to change the diagnosis and direct therapy?

microbiology reports

4

Reference ranges are based on

range of values determined by large numbers of normal, healthy individuals (may be age, sex, race specific)

5

Reference range is calculated by

mean value and the standard deviation

6

Reference range is a ____________ curve

bell-shaped, Gaussian ST of +/-2 to include 95%

7

Total bilirubin reference range curve

Non-Gaussian

8

Total serum cholesterol reference range

is a "healthy" rand based on epidemiological studies

9

Serum creatinine is a good example of

the necessity of comparing current value to previously determined value

10

Endocrinology tests reference ranges are based on

stimulatory and inhibitory recordings

11

In disease prognosis/progression it is important to

monitor change sin value (not reference range) i.e.. LDL, PSA

12

What is the chance of an abnormal result if you do 1 test?
2 ind tests?
5 ind tests?
10 ind tests?

5%
10%
23%
40%

13

Action levels

abnormal result that ay or may not require treatment, cholesterol > 200, LDL > 160, HDL < 35 --> patient should be more active

14

Sensitivity

probability that a patient with a disease will test positive

15

Sensitivity equation

Sn = 100X TP/ (TP + FN)

16

Specificity

probability that a non-diseased patient will test negative

17

Specificity equation

Sp = 100X TN / (TN + FP)

18

Prevalence

pre-test probability of disease in the population

19

Altering the sensitivity will

alter the specificity of a test and vice versa

20

Choose a test with HIGH Sensitivity when

the probable disease is serious and curable

21

Want a very sensitive test when the

benefit of detecting the disease are great

22

Choose a test with a HIGH specificity when

the probable disease is serious but not treatable

23

Want a highly specific test when the

risks of wrong diagnosis is great

24

Confirmatory test

highly sensitive

25

Common order of testing

sensitive tests followed by specific

26

PPV

probability that a positive test result indicates disease

27

PPV equation

PPV= 100X TP/ (TP + FP)

28

NPV

probability that a negative test result indicates no disease

29

NPV equation

NPV= 100X TN/ (TN + FN)

30

Does prevalence effect the predictive value?

Yes, the less prevalent a disease the lower the PPV. Higher prevalence = higher PPV

31

Does sensitivity and specificity effect predictive value?

Yes, the more sensitive/specific, the higher the PPV.

32

Serial testing effect on sensitivity

decreases

33

Serial testing effect on specificity

increases

34

Parallel testing effect on sensitivity? specificity?

higher sensitivity, lower specificity

35

What test would you use for a mild treatable disease?

good sensitivity and specificity

36

Order of testing for clinicians

high sensitivity test followed high by specificity test

37

Once prevalence reaches >50% what effect does it have on predictive value

not much increase in predictive value

38

Is predictive value effected by cut-off values

Yes, cut off values change the sensitivity and specificity of a test and therefore change the PPV and NPV

39

Pre-analytic errors

medication interference, wrong patient prep, inadequate amt of specimen, wrong specimen, delayed transport, wrong storage

40

Pre-analytic variation

age, gender, mass, prep of patient, posture of patient, specimen type

41

Analytic errors

wrong usage of equipment, expired reagents

42

Analytic variables

analytical sensitivity, analytical specificity, analytical interference, precision, accuracy, drug impact, lab instruments

43

Analytical sensitivity

ability to detect a substance; least concentration measurable by the test (high... PCR)

44

Analytical specificity

ability to detect only 1 substance;

45

Precision

reproducible

46

accuracy

closeness to a known accepted value

47

Post-analytical errors

wrong results, time delays

48

Physician Factors influencing decision to order tests

faulty decision-making, over reliance, lack of understanding, lack of appreciation of testing limitations, etc

49

Laboratory Factors influencing decision to order tests

convenience of automation, rapid, new tests without proven results, etc

50

Medical Science factors influencing lab tests

new treatments that require monitoring

51

Patient and Societal factors influencing lab tests

expectations, health ins, etc

52

Hospital factors influencing lab tests

encouragement, ICU and dialysis centers, decreased length of stay, more severely ill patients