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cv > Test Validation > Flashcards

Test Validation Flashcards

1
Q

What is the purpose of validation?

A

To establish the truthfullness.

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2
Q

What is a test compared to?

A

a “gold standard” for accuracy.

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3
Q

Gold standards used for VU comparison are typically what?

A
  • Angiography
  • CTA
  • MRA
  • Pathology
  • Re-test same day/ different tech (DVT)
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4
Q

What are the 4 steps in a test validation process?

A
  1. Question defined.
  2. Data log created and completed.
  3. Calculate the statistics.
  4. Report te statistics.
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5
Q

How should you define the question?

A
  • Presence of disease.
  • Severity of disease.
  • Location of disease as defined.
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6
Q

How should a data log be designed?

A
  • Set time limit for data
  • Set population description.
    • ie. patients with no intervention in carotid.
  • Set parameters to be collected.
    • log according to diagnostic criteria grade as indicated in the conclusion.
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7
Q

What are some tips for collecting data?

A
  • Stay blinded to the opposite test while completing log.
  • Keep a list of ALL exams thrown out.
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8
Q

When is a matrix used?

A

It is used when there are more than 2 categories for test results.

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9
Q

What are 3 parts of a matrix statistics?

A
  1. precent agreement
  2. percent overestimated
  3. percent underestimated.
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10
Q

What is the percent agreement?

A

Diagonal boxes on diagram.

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11
Q

How do you find the percent agreement?

A

(# matched)/(total)

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12
Q

What is the percent overestimated?

A

Duplex hugher grade than angio.

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13
Q

How do you find the percent overestimated?

A

(# overestimated)/(total)

*above diagonal

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14
Q

What is the percent underestimated?

A

Duplex lower grade than angio.

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15
Q

How do you find the percent underestimated?

A

(# underestimated)/(total)

*above diagonal.

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16
Q

When can more specific statistics be used?

A

If only two answers are possible to answer the question,

17
Q

What positive/negative statistic is used to answer this question:

What percentage of patients who come to the lab with disease do you identify as having disease?

A

Sensitivity (SENS)

18
Q

What positive/negative statistic is used to answer this question:

What percentage of normal patients can your testing identify as normal?

A

Specificity (SPEC)

19
Q

What positive/negative statistic is used to answer this question:

Of all the patients with positive test results (with disease), what percentage actually have disease?

A

Positive Predicitve Value (PPV)

20
Q

What positive/negative statistic is used to answer this question:

Of all the negative test results (normal) that your lab reports what percentage of those are actually normal?

A

Negative Predictive Value (NPV)

21
Q

What positive/negative statistic is used to answer this question:

What is the overall accuracy of your lab results?

A

Overall Accuracy (OA)

22
Q

If both gold standard angio and duplex match what does it indicate?

A

True positive.

23
Q

If both standards dont match what does it indicate?

A

True negative.

24
Q

If the gold standard for angio is negative, and for duplex is positive, then what does it indicate?

A

False positive.

25
Q

If the gold standard for angio is positive and for duplex is negative, what does it indicate?

A

False negative.

26
Q

How do you calculate the sensitivity?

A

TP/ALL positive angios

27
Q

How do you calculate specificity?

A

TN/ALL negative angios

28
Q

How do you calculate PPV?

A

TP/ALL positive duplex

29
Q

How do you calculate NPV?

A

TN/ALL negative duplex.

30
Q

How do you calculate the OA?

A

TP+TN/Total Comparison

31
Q

What number does the Overall Accuracy (OA) yield?

A

A number between the sensitivity and specificty and between the PPV and NPV

32
Q

What is sensitivity?

A

The ability to idenitfy disease in all patients who are tested with the disease.

33
Q

What is specificity?

A

The ability to identify patients without the disease in all patients tested without the disease.

34
Q

What is PPV?

A

The probability that a single positive duplex result is truly positive by the gold standard.

35
Q

What is NPV?

A

The probability that a single negative duplex result is truly negative by the gold standard.

cv (16 decks)

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