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Clin Lab > Day 1 > Flashcards

Day 1 Flashcards

1
Q

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

A
  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
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2
Q

What do unnessisary tests do?

A
  • Hurt patient financially
  • Can be inconvenient
  • Wasted or misleading information
  • Loss of time
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3
Q

What are multichannel chemical analyzers?

A

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

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4
Q

Tests should be ordered to _______

A
  • Confirm a diagnosis based on the entire clinical picture (history and clinical presentation)
  • Or if the result will alter therapy decisions
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5
Q

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

A

Sensitivity

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6
Q

T/F- False negatives are found in sensitive test

A

True

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7
Q

What does a test that has 90% sensitivity mean?

A

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

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8
Q

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)

A

Specificity

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9
Q

Specific tests sometimes show….

A

False Positives

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10
Q

Describe false positives…

A

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

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11
Q

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

A

Prevalence

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12
Q

Describe predictive value

A

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

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13
Q

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

A

Low

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14
Q

How is predictive value applied to lab test?

A

Predictive value evaluates the reliability of a positive or negative result

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15
Q

What 2 things are used to establish predictive value?

A

The sensitivity and specificity of the test in question

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16
Q

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

A

True

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17
Q

This is what the test in question is compared to

-The best test

A

Gold Standard

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18
Q

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

A

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

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19
Q

Reliability of laboratory tests is affected by…

A

Technical performance in the lab

20
Q

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

A

Reproducibility

21
Q

What factors influence reproducibility

A
  • Experience of technicians
  • reagents involved
  • equipment used
22
Q

How is variation of the mean expressed?

A

Standard deviation

23
Q

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

A

Coefficient of variation

24
Q

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

A

Lower accuracy, lesser reproducibility

25
Q

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

A

4%

26
Q

What does the coefficient of 4% mean?

A

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

27
Q

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

A

2

28
Q

A deviation of ___% is deemed technically acceptable

A

8%

29
Q

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

A

Accuracy

30
Q

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

A

Compare it to the assay

31
Q

What happens in a random inaccuracy?

A

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

32
Q

What are examples of random inaccuracies?

A
  • 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
Q

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

A

Repeat the tests

34
Q

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

A

True

35
Q

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

A
  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
Q

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

A

Nope!

37
Q

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

A

68%

38
Q

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

A

95%

39
Q

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

A

99.7%

40
Q

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

A

2.5% above and 2.5% below

41
Q

What if clinically normal people have undetected disease?

A

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
Q

What factors may effect results in non-diseased patients?

A
  • Age
  • Sex
  • Race
  • Diet
  • Posture
  • Specimen storage time
43
Q

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

A

Greater

44
Q

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

A

Greater

45
Q

Instead of the word normal, use the word…

A

Reference range

Clin Lab (23 decks)

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