Sensitive/specificity/PPV/NPV/incidence/prevelance Flashcards

0
Q

Sensitivity is also called

A

True positive rate

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1
Q

Fixed properties of a test

A
  1. Sensitivity

2. Specificity

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2
Q

Evaluation of a diagnostic test

A

Uses 2X2 table comparing test results with te actual presence of disease (vertical: TEST: + - / horizontal: disease: + -)

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3
Q

Sensitivity equation

A

TP/(TP+FN)=1-FN rate

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4
Q

Sensitivity - definition

A

Proportion of all people with disease who test positive or,

The probability that a test detects disease when disease is present

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5
Q

Value approaching 100% sensitivity is desirable for ruling …. disease
It indicates

A

OUT

A low false negative rate

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6
Q

High sensitivity test used for screening in disease with ….. prevalence

A

LOW

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7
Q

Specificity is also called

A

TN rate

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8
Q

Specificity

A

Proportion of people without disease who test negative
or,
The probability that a test indicates non disease when disease is absent

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9
Q

Value approaching 100% specificity is desirable for ruling …. disease
and indicates a

A

IN

Low false positive rate

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10
Q

High specificity test used for

A

Confirmation after a positive screening test

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12
Q

Positive predictive value

A
  1. Proportion positive test that are true postive

2. Probability that person actually has the disease given a positive test result

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12
Q

Positive predictive value equation

A

TP/(TP+FP)

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13
Q

PPV varies directly with

A

Prevalence or pretest probability

High pretest –> high PPV

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14
Q

Negative predictive value

A
  1. Proportion of negative test results that are true negative
  2. Probability that person actually is disease free given negative test result
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15
Q

Negative predictive value equation

A

TN/(FN+TN)

16
Q

NPV varies inversely with

A
  1. Prevalence
  2. Pretest probability
    High pretest probability –> low NPV
17
Q

Prevalence

A

Number of existing cases/number of people at risk

At a point in time

18
Q

Incidence rate

A

(Number of new cases in a specified time of period)/(population at risk during same time)

19
Q

Prevalence directly reversible

A
  1. Incidence

2. Average disease dutation

20
Q

Incidence and prevalence in common cold. Bigger?

A

Very similar because duration is short

21
Q

Incidence and prevalence in chronic diseases. Bigger?

A

Prevalence. Long duration

22
Q

Posspitive and negative predictive value vary depending on

A

Disease prevalence

23
Q

Specificity equation

A

TN=TN/TN+FP

= 1-FP

25
High sensitivity test used for
SCREENING in diseases with LOW prevalence
26
town population is 7.500. In 2011, 200 residents diagnosed with RA. in 2012, 100 more residents are discovered by RA. incidence, prevalence?
``` incidence = 100/7300 prevelance = 300/7500 ```
27
fixed properties of a test and properties that vary
fixed: specificity, sensitivity vary: PPV, NPV (depending on disease prevalence)
28
association between PPV, NPV, sensitivity, specificity
high sensitivity --> high NPV | high specificity --> high PPV