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MRCPsych Part B > Evaluating Prognosis > Flashcards

Evaluating Prognosis Flashcards

1
Q

What studies are used to estimate prognosis?

A

Cohort studies
RCTs

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2
Q

X and Y axis to evaluate prognosis

A

X: Time
Y: proportion surviving i.e. not attaining an ‘event’

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3
Q

What is displayed at each point on a graph?

A

Cumulative probability of an individual remaining free of event/outcome

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4
Q

What is the name of the curve for evaluating prognosis?

A

Kaplan-Meier Survival Curves

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5
Q

What does it mean if observations are censored?

A

Not all subjects will have reached the outcome by that period of time

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6
Q

What does left censored mean?

A

Observations began after some events have occurred (missed past events)

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7
Q

What does right censored mean?

A

Observation was terminated before events could be observed (missed future events)

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8
Q

Why can we not calculate the mean survival time from studies?

A

Due to censoring we do not know the actual survival times beyond the end of the study period

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9
Q

What is the median survival time?

A

The survival time of 50% of observed sample

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10
Q

How can one compare survival rates of two samples?

A

Log-rank test

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11
Q

What type of test is log-rank test?

A

Non-parametric

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12
Q

What can log-rank test not be used for?

A

To account or adjust for effects of other variables

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13
Q

How does one study multiple variables in survival studies?

A

Cox regression analysis

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14
Q

What type of test is cox regression analysis?

A

Semiparametric

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15
Q

Why is cox regression analysis called proportional hazard

A

It assumes that the effects of multiple variables are constant over a period of time

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16
Q

What does log-rank test inform us?

A

Whether significant differences are present between two survival curves
Does not measure magnitude

17
Q

What tells us the size of difference between two survival curves?

A

Hazard ratio

18
Q

What can Mantel-Haenszel test be used for in survival studies?

A

To study effect of two binary independent variables on outcome

19
Q

Method used if one categorical IV and continuous DV

A

Kaplan-Meier curve with log-rank test

20
Q

Method used if >1 categorical IV and continuous DV

A

Cox’s proportional hazard

21
Q

Method used if 2 categorical IV and continuous DV

A

Mantel-Haenszel test

22
Q

Questions to ask re validity of results in a prognostic study

A

Was sample representative?
Were patients similar to each other with respect to prognostic factors?
Was follow-up sufficiently complete?
Were outcome criteria objective and unbiased?

23
Q

How to determine if sample of patients is representative

A

If they go through a filter, likely they will be different from population of interest

24
Q

How to test if patients were similar to each other with respect to prognostic factors

A

If study includes patients at different stages of the disease, survival estimates of the group will not be applicable to each group member

25
Q

Questions to ask about the results in prognostic studies

A

How likely are outcomes over time?
How precise are the estimates of likelihood?

26
Q

How does one analyse the likelihood of outcomes over time?

A

Kaplan-Meier curve

27
Q

How does one analyse the preciseness of estimates of likelihood>

A

Survival curves are more precise in earlier periods, indicated by narrower confidence bands around left-hand parts of curve

28
Q

Why are survival curves more precise at earlier periods?

A

Due to losses to follow-up

29
Q

Questions to ask when considering if results from prognostic study can be applied to patient care

A

Were study patients and clinical context similar to mine?
Was follow-up sufficiently long?

30
Q

Endpoints of survival curves

A

Death during trial
Loss to follow-up
Still alive at end (right censor)
Adverse event
Discontinuation of treatment

31
Q

How long does recruitment take for prognostic studies?

A

2-3 years

32
Q

At what point in a prognostic study is there likely to be significant attrition?

A

If minimum follow-up is 5 years

33
Q

What is the focus in survival curves?

A

Time to end-point

34
Q

What does poor median survival mean in a survival curve?

A

Worse early prognosis but better late prognosis

35
Q

What does representative median survival mean?

A

No comparable differences in early and late periods of disease

36
Q

What does impressive median survival imply?

A

Good early prognosis but poor later prognosis

MRCPsych Part B (64 decks)

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