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STATISTICS - STEP 2 > FA > Flashcards

FA Flashcards

1
Q

Clinical trial - definition

A

Experimental study involving humans. Compares therapeutic benefits of 2 or more treatments, or the treatment and placebo

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2
Q

Double blinded study

A

Neither patient nor doctor knows whether the patient is in the treatment or control group

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3
Q

Triple blind refers to

A

The additional blinding of the researchers analyzing data

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4
Q

Clinical trial study quality improves when study is

A
  1. Randomized
  2. Controlled
  3. Double blinded
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5
Q

Clinical trial phase 1 sample

A

Small number of healthy volunteers or patients with disease of interest

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6
Q

Clinical trial phase 1 purpose

A

Assesses

  1. safety (is it safe?)
  2. toxicity
  3. pharmacokinetics
  4. Pharmacodynamics
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7
Q

Clinical trial phase 2 sample

A

Small number of patients with disease of interest

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8
Q

Clinical trial phase 2 purpose

A

Assess treatment

  1. efficacy (does it work?)
  2. optimal dosing
  3. adverse effects
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9
Q

Clinical trial phase 3 sample

A

Large number of patients randomly assigned either to the treatment under investigation or the best available treatment (or placedo)

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10
Q

Clinical trial phase 3 purpose

A

Compares the new treatment to the current standard of care (is it as good or better?)

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11
Q

Clinical trial phase 4 sample

A

Postmarketing surveillance trial of patients after approval

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12
Q

Clinical trial phase 4 purpose

A

Detects rare or long term adverse effects. Can result in a drug withdrawn from market (can it stay?)

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13
Q

Types of studies

A
  1. Cross-sectional study
  2. Case-control study
  3. Cohort study
  4. Twin concordance
  5. Adoption study
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14
Q

Adoption study design

A

Compares sibling raised by biological vs adoptive parents

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15
Q

Adoption study measures

A

Heritability and influence of environmental factors

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16
Q

Twin concordance study measures

A

Heritability and influence of environmental factors (nature vs nurture)

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17
Q

Twin concordance study design

A

Compares frequency with which both monozygotes twins or both dizygotic twins develop same disease

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18
Q

Cross-sectional study type

A

Observational

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19
Q

Cross-sectional study design

A

Collects data from a group of people to assess frequency of disease and related factors at a particular point in time (disease PREVALENCE)

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20
Q

Cross-sectional study/ask

A

What is happening?

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21
Q

Case control study type

A

Observational and retrospective

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22
Q

Cross-sectional study measures

A
  1. Disease prevalence

2. Can show risk factor association with disease (but does not establish causality)

23
Q

Case control study/asks

A

What happened

24
Q

Case control study design

A
  1. Compares a group of people with disease to a group without disease
  2. Look for prior exposure or risk factors
25
Q

Case control study measure

A

Odds ration (OR)

26
Q

Case control study example (copd-smoking)

A

Patients with copd had higher odds of a history of smoking than those without copd

27
Q

Cohort study type

A

Observational and prospective or retrospective

28
Q

Cohort study design

A
  1. Compares a group with a given exposure of risk factor to a group without such exposure
  2. Looks to see if exposure increases the likehood of disease
  3. Can be prospective (who will develop the disease) or retrospective (historical) (who developed the disease)
29
Q

Cohort study measure

A

Relative risk

30
Q

Cohort study/ask

A

Who developed the disease
Or
Who will develop the disease (exposed vs not

31
Q

Cohort study example (copd/smoker)

A

Smokers had a higher risk of developing copd than nonsmokers

32
Q

Clinical treatment trials - type of study (why)

A

cohort study –> some members with a specific illness are given one treatment and other members are given another treatment or placebo

33
Q

Fixed properties of a test

A
  1. Sensitivity

2. Specificity

34
Q

Sensitivity - definition (and equation)

A

Proportion of all people with disease who test positive or,
The probability that a test detects disease when disease is present
TP/(TP+FN)=1-FN rate

35
Q

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

A

LOW

36
Q

Specificity - definition (and equation)

A

Proportion of people without disease who test negative
or,
The probability that a test indicates non disease when disease is absent
TN/(TN+FP)=1-FP rate

37
Q

100 sensitivity vs specificity - rule in vs rule out

A

sensitivity - rule out (low FN rate)

specificity - rule in (low FP rate)

38
Q

Positive predictive value - definition (and equation)

A
  1. Proportion positive test that are true postive
  2. Probability that person actually has the disease given a positive test result
    TP/(TP+FP)
39
Q

PPV varies directly with

A

Prevalence or pretest probability

High pretest –> high PPV

40
Q

Negative predictive value - definition (and equation)

A
  1. Proportion of negative test results that are true negative
  2. Probability that person actually is disease free given negative test result
    TN/TN+FN
41
Q

NPV varies inversely with

A
  1. Prevalence
  2. Pretest probability
    High pretest probability –> low NPV
42
Q

fixed properties of a test and properties that vary

A

fixed: specificity, sensitivity
vary: PPV, NPV (depending on disease prevalence)

43
Q

association between PPV, NPV, sensitivity, specificity

A

high sensitivity –> high NPV

high specificity –> high PPV

44
Q

Likelihood ratio?

A

likelihood that a given test result would be expected in a patient with the target disorder compared to the likelihood that the same result would be excepted in a patient without the target disorder

45
Q

positive likelihood ratios indicate

A

LR+ = sens / (1 - spec) = TP/FP –> probability of an individual with the condition having a positive test / probability of an individual without the condition having a positive test

46
Q

negative likelihood ratios indicate

A

LR- = (1-sensit) / specif) FN/TN–> probability of an individual with the condition having a negative test / probability of an individual without the condition having a negative test

47
Q

Number of LR in very useful diagnostic tests

A

LR+ grearer than 10

LR- lower than 0.1

48
Q

how to estimate posttest odd

A

multiple LR with pretest odds

49
Q

Prevalence

A

Number of existing cases/number of people at risk

At a point in time

50
Q

Incidence rate

A

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

51
Q

Prevalence directly reversible

A
  1. Incidence

2. Average disease dutation

52
Q

Incidence and prevalence in common cold. Bigger?

A

Very similar because duration is short

53
Q

Positive and negative predictive value vary depending on

A

Disease prevalence

54
Q

town population is 7.500. In 2011, 200 residents diagnosed with RA. in 2012, 100 more residents are discovered by RA. incidence, prevalence?

A 
incidence = 100/7300
prevelance = 300/7500

STATISTICS - STEP 2 (6 decks)

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