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Flashcards in Day 1 Deck (45):
1

When considering a lab test, what are some things you should take into consideration before you order it?

1. Is the test just information or diagnostic
2. If 2 tests give you the same information, when should one be used before another?
3. What are disadvantages and possibilities of errors or false results

2

What do unnessisary tests do?

-Hurt patient financially
-Can be inconvenient
-Wasted or misleading information
-Loss of time

3

What are multichannel chemical analyzers?

Take a large number of tests and have the results back in a short time
-Came back that this wasn't very helpful for diagnosing disease in asymptomatic patients

4

Tests should be ordered to _______

-Confirm a diagnosis based on the entire clinical picture (history and clinical presentation)
-Or if the result will alter therapy decisions

5

This is the ability of a test to detect patients with a specific disease

Sensitivity

6

T/F- False negatives are found in sensitive test

True

7

What does a test that has 90% sensitivity mean?

That in 10% of patients with the disease, the test will not detect it

8

This describes how well the test abnormality is restricted to those patients that have the disease in question (that it picks up on the sign due to that specific disease)

Specificity

9

Specific tests sometimes show....

False Positives

10

Describe false positives...

A specificity of 90% for disease X indicates that 10% of the test results suggestive of disease X aren't due to disease X

11

This is the incidence of disease (number of people with the disease) in the population being tested

Prevalence

12

Describe predictive value

The smaller the number of people with a disease, the lower the proportion of people with an abnormal test, and the greater the proportion of false positives

13

If you wouldn't believe a test, it has a high/low predictive value

Low

14

How is predictive value applied to lab test?

Predictive value evaluates the reliability of a positive or negative result

15

What 2 things are used to establish predictive value?

The sensitivity and specificity of the test in question

16

T/F- To establish predictive value you need a reference method for diagnosis to be available other than the test being evaluated?

True

17

This is what the test in question is compared to
-The best test

Gold Standard

18

If it is not possible to detect patients with a certain disease...

Its not possible to provide a truly accurate calculation of sensitivity, specificity, and predictive value

19

Reliability of laboratory tests is affected by...

Technical performance in the lab

20

The measure of how closely the lab can approach the same answer when the test is repeatedly performed with the same sample

Reproducibility

21

What factors influence reproducibility

-Experience of technicians
-reagents involved
-equipment used

22

How is variation of the mean expressed?

Standard deviation

23

When the standard deviation is converted to a percentage of the mean value, this is called?

Coefficient of variation

24

The higher the coefficient of variation, the higher/lower the accuracy, greater/lesser reproducibility?

Lower accuracy, lesser reproducibility

25

Reproducibility is demonstrated with the coefficient of variation of ___ %?

4%

26

What does the coefficient of 4% mean?

That 68% of values are within 1 standard deviation (4% above and 4% below the true value)

27

+/- ___ standard deviations is used to define acceptable limits?

2

28

A deviation of ___% is deemed technically acceptable

8%

29

This is the correct answer, and the result that the assay should produce

Accuracy

30

How does the lab figure out the accuracy of a test?

Compare it to the assay

31

What happens in a random inaccuracy?

-Random inaccuracies may not effect all of the specimens and therefore may have not altered the control specimens

32

What are examples of random inaccuracies?

-Specimen from the wrong patient
-Specimen hemolysis
-Insufficient mixing
-Clerical errors (patients with the same last name)
-Decimal point errors
-Transcription of results into the wrong charts

33

If unexpected test results are seen, what should you do first?

Repeat the tests

34

T/F- Normal range is a concept that considers all tests within the normal range to be normal and anything outside the normal range to be abnormal

True

35

What are the 2 premises involved in establishing the normal range?

1. Assume that all patients do not demonstrate clinical signs and symptoms that are normal
2. Assume that test results from those people considered normal will have random distribution

36

Are any factors that would bias a significant group toward either the high or low side included?

Nope!

37

What percentage of values fall in +/- 1 standard deviation?

68%

38

What percentage of values fall within +/- 2 standard deviations?

95%

39

What percentage of values fall within +/- 3 standard deviations?

99.7%

40

If 2 standard deviations are accepted, what percentage of clinically normal people will have values above and below this range?

2.5% above and 2.5% below

41

What if clinically normal people have undetected disease?

They will influence the normal range so...
-you have to take the top values or the lowest values and run their labs again using the gold standard tests to see if they are in fact normal- if not, they are outta hereee and you made your normal range more accurate

42

What factors may effect results in non-diseased patients?

-Age
-Sex
-Race
-Diet
-Posture
-Specimen storage time

43

The greater number of tests employed, the greater/lesser the chance that at least one will yield a false result?

Greater

44

The farther away the values are from the normal limits, the greater/lesser the likelihood of a true disease

Greater

45

Instead of the word normal, use the word...

Reference range