88 - Stats Revision Flashcards

1
Q

How can sensitivity/specificity be ascertained?

A

Compare performed test to ‘gold standard’ test.

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2
Q

Positive predictive value

A

Of all positive tests, what proportion are truly positive

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3
Q

Negative predictive value

A

Of all negative tests, what proportion are truly negative

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4
Q

Measures of the accuracy of a test

A

Sensitivity and specificity (inherent to a test and are constant)

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5
Q

What are PPV and NPV dependent on?

A

Sensitivity and specificity.

Prevalence of outcome.

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6
Q

What can make PPV appear really low, even though specificity can be high?

A

If a disease is rare enough. The number of false positives can overwhelm the number of true positives, as the number of negative cases is so much higher than positive cases.

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7
Q

What does PPV positively correlate with?

A

Underlying prevalence of disease

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8
Q

What does the utility of a diagnostic test rely on?

A

The underlying prevalence of disease (because is related to PPV)

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9
Q

When do you order diagnostic tests?

A

When there is a strong clinical suspicion of disease.

Because test relies on underlying prevalence of disease.

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10
Q

When are diagnostic tests not used?

A

To screen for diseases.

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11
Q

Who are targeted for screening tests?

A

Those with high risk of outcome of interest.

EG: Mammography on women over 50

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12
Q

Why wouldn’t you use a diagnostic test to screen for disease?

A

Because the underlying prevalence of a disease that is screened for with a diagnostic test is low. This means that the PPV will be low, and the chance of a true positive result is overwhelmed by the chance of a false positive result.

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13
Q

What is biostatistics concerned with, w/r/t samples?

A

The extent to which the study (sample) results reflect the ‘truth’

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