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Epidemiology Exam 2 > Chapter 5(from in class packet) > Flashcards

Chapter 5(from in class packet) Flashcards

1
Q

why do we screen for disease?

A

to detect disease before there are signs or symptoms in order to REDUCE morbidity and mortality rates

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2
Q

What is screening?

A

the application of a disease-detection test to people who are as yes asymptomatic

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3
Q

What is the purpose of screening?

A

to classify individuals with respect to their likelihood of having a particular disease

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4
Q

Can screening tests also be used as diagnostic tests?

A

YES

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5
Q

Diagnosis involves what?

A

involves CONFIRMATION of PRESENCE or ABSENCE of disease in someone suspected or at risk of disease

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6
Q

Screening is generally done among what type of individuals?

A

individuals who ARE NOT SUSPECTED of having disease

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7
Q

What are some popular screening tests?

A
  • mammography
  • colonoscopy
  • fecal occult
  • pap smear
  • PPD
  • A1C
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8
Q

What are the requirements for a Screening Test?

A
  • should be relatively SENSITIVE and SPECIFIC
  • should be simple and INEXPENSIVE
  • should be VERY SAFE
  • must be ACCEPTABLE to subjects and providers
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9
Q

People who are being screened are?

A
  • generally NOT patients
  • NOT sick
  • AREN’T expecting treatment
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10
Q

What are the General Principles of Screening (by WHO)?

A
  1. the condition should be an IMPORTANT health problem
  2. there should be a TREATMENT for the condition
  3. FACILITIES for diagnosis and treatment should be available
  4. there should be a LATENT STAGE of the disease
  5. there should be a TEST or EXAMINATION for the condition
  6. the test should be ACCEPTABLE to the population
  7. the natural HISTORY of disease should be ADEQUATELY UNDERSTOOD
  8. there should be an AGREED POLICY on whom to treat
  9. the total cost of finding a case should be ECONOMICALLY BALANCED in realtion to medical expenditure as a whole
  10. Case-finding should a CONTINUOUS PROCESS not just a “once and for all” project
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11
Q

How good is the test?

A

should be VALID and RELIABLE

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12
Q

What is the term that asks, “How well does the test measure what it is supposed to measure?”

A

validity

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13
Q

Reliability is what?

A

REPEATABILITY

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14
Q

What is the term that asks, “How well does the test do in different populations?”

A

reliability

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15
Q

What is seen in the “perfect world”?

A

TRUE POSITIVES AND TRUE NEGATIVES

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16
Q

What is seen in the “real world”?

A

FALSE POSITIVES AND FALSE NEGATIVES

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17
Q

People who are NOT diseased but have a POSITIVE test

A

FALSE POSITIVE

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18
Q

People who really HAVE disease, but have a NEGATIVE test

A

FALSE NEGATIVE

19
Q

ability of the test to identify those who are diseased in the screened population

A

sensitivity

20
Q

the ability of the test to identify those who do not have the disease

A

specificity

21
Q

What is the overall accuracy of the test?

A

TP+TN/ TP+TN+FP+FN

22
Q

Sensitivity should be INCREASED when?

A
  • the penalty associated with missing a case is high
  • the disease can be spread
  • subsequent diagnostic evaluation are associated with minimal cost and risk
23
Q

Specificity should be INCREASED when?

A
  • the costs or risks associated with further diagnostic techniques are substantial
  • minimize false positives
24
Q

True or False. Sensitivity and specificity are able to predict the performance of the screening test in the population.

A

FALSE because sensitivity and specificity are NOT able to predict

25
Q

the probability that a person actually has the disease given a positive test

A

positive predictive value (PPV)

26
Q

the probability that a person do not have the disease given a negative test

A

negative predictive value (NPV)

27
Q

What is a predictive value?

A

measures whether or not an individual actually has the disease, given the results of a screening test

28
Q

What are the 3 things predictive value is affected by?

A
  • specificity
  • prevalence of preclinical disease
  • sensitivity
29
Q

during sequential screening, if you take all the people who screened positive on the first test and give them a second test (of higher sensitivity and specificity) what happens to the net?

A
  • net sensitivity decreases

- net specificity increases

30
Q

true or false. the ppv is maximized when used in “high risk” populations since the prevalence of the pre-clinical disease is higher than in the general population

A

true

31
Q

screening the general population for a relatively infrequent disease can be what?

A
  • wasteful of resources and may yield few previously undetected cases
32
Q

a test must be _____ before it can be valid

A

reliable

33
Q

an invalid test can demonstrate ________ ________

A

high reliability

34
Q

what are the three sources of variation?

A
  1. instrument variation
  2. inter- observer variation
  3. intra-subject variation
35
Q

the need for calibration or standardization

A

instrument variation

36
Q

changes in repeated bp measurements over TIME

A

intra-subject variation

37
Q

inconsistency of interpretation by two or more diagnosticians

A

inter-observer variations

38
Q

what is the deviation of the results from the truth?

A

bias

39
Q

what is the interval between “diagnosis” of disease at screening and when it would have been detected from clinical symptoms?

A

lead time bias

40
Q

to detect disease before there are signs or symptoms in order to reduce morbidity and mortality from disease

A

lead time bias

41
Q

do you increase life expectancy for lead time bias?

A

no, you just cause the disease early

42
Q

the average length of time a person lives after the diagnosis with the disease or condition

A

survival time

43
Q

What kind of bias is this: “volunteers may be healthier than people who don’t volunteer”?

A

self selection bias

44
Q

What kind of bias is this: “persons who screen positive who are really disease free can be erroneously diagnosed with a disease, resulting in a more favorable long term outcome. results in the appearance of effective screening”?

A

over diagnosis bias

Epidemiology Exam 2 (5 decks)

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