k - 4 scenario prognosis.ppt
TRANSCRIPT
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Scenario:
You see a 70 year old man in an outpatientclinical 3 months after he has been dischargedfrom your service with a cerebral infarctionstroke. He is in sinus rhythm, has mild residual
left-sided weakness but is otherwise well. Hisonly medication is aspirin and he has noallergies. He recently saw an article on the BMJwebsite describing the risk of seizure after acerebral infarction and is concerned that this willhappen to him.
Please try to answer the question as best as youcan!
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2
Task
Read it and decide:
Whether it answers your question.
If so, what that answer is.
What you will tell the patient
EBM WAYVALIDITY
IMPORTANCE
APPLICABILITY
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3
EBM Process
Patient
Encounter
Formulating the
Clinical Question
Searching the
Evidence
Appraising the
Evidence
Diagnosis
Therapy
PrognosisEtiology
Patient
Intervention
Comparison
Outcome
Hierarchy of evidence
Pre appraised resources
Drawing conclusion
That impact on practice
DOE
POE
(Lang, 2000)
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4
PICO
P I C O
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5
PICO
P I C OPatients with
a history of
cerebralinfarct stroke
Risk of
seizure
within 5years
Keyword: stroke, seizure
Formulating questions:
IN patients with a history of cerebral infarct stroke, what is the risk of
seizure within 5 years?
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Epileptic seizures after a first
stroke: the Oxford shire
community stroke project
John Burn et all, BMJ 1997;3715: 1582-
Example : an article of prognostic test, entitle :
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Background: Cerebrovasculer disease is an important cause of
epilepsy, particularly in elderly people. When seizures complicate a clinical stroke they have a
devastating effect on morale and further impair an
already compromised quality of life.
Precise estimates of the risk of developing epilepsywould be helpful not only to patients but also to those
who give advice on returning to work or driving.
Objectives: To describe the immediate and long term risk of epileptic
seizures after a first ever stroke
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Study Design:
Cohort study following up stroke survivors for 2 to 6.5
years; comparison with age specific incidence rates of
epileptic seizures in the general population.
Setting: Community based stroke register
Subjects: 675 patients with a first stroke, followed up for
a minimum of 2 years
Main outcome measures: occurrence of single and
recurrent seizures
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Table 3 Cumulative actuarial risks (95% confidence intervals) of experiencing a
seizure after stroke by type of first stroke (19 patients with a history of prestroke
seizures were excluded)
Time
after
stroke
Cerebral
infarction
Primary
intracerebral
haemorrhage
Subarachnoid
haemorrhageTotal
1 year 4.2 (2.2 to 6.2) 19.9 (1.5 to 38.3) 22.0 (2.6 to 41.8) 5.7 (3.5 to 7.9)
2 years 6.7 (4.1 to 9.3) 19.9 (1.5 to 38.3) 27.8 (5.3 to 50.7) 8.2 (5.4 to 11.0)
3 years
7.4 (4.0 to
10.8) 26.1 (2.2 to 50.0) 34.3 (8.0 to 62.0) 9.5 (5.8 to 13.2)
4 years
8.6 (4.5 to
12.7) 26.1 (1.3 to 50.9) 34.3 (2.0 to 68.1) 10.5 (6.0 to 15.0)
5 years
9.7 (3.7 to
15.7) 26.1 (0 to 54.8) 34.3 (0 to 100) 11.5 (4.8 to 18.2)
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Was a defined, representative sample
of patients assembled at a common
(usually early) point in the course of
their disease?
Yes - from a common point but unsure
how GPs decided which stroke
patients should be admitted to hospital
Was patient follow-up sufficiently long
and complete?
Yes-minimum of 2 years and up to 6.5
years
Were objective outcome criteria
applied in a "blind" fashion?
Patients were asked at follow-up if
they had a seizure and were then
assessed by a study neurologist
(unsure if neurologist was blinded)
If subgroups with different prognoses
are identified, was there adjustmentfor important prognostic factors?
looked at different stroke types,
previous history of stroke
Was there validation in an
independent group ("test-set") of
patients?
NO (there was no pre study intention)
Are the result valid?
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Are the valid results of the prognosis study
important?
How likely are the outcomes overtime?
4.2% over one year
How precise are the prognostic
estimates?
95% confidence interval
2.63 to 5.77
Calculation:N = 545
P = 4.2 %
SE = 0.042 x (1-0.042)
545
= 0.008
= 0.8 %
95% CI = 4.2% (1.96 x 0.8%)
= 4.2%
1.57%= 2.63 to 5.77
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Can you apply this valid, important evidence about
prognosis in caring for your patient?
Were the study patients similar to
your own?
YES
Will this evidence make a clinically
important impact on your conclusions
about what to offer or tell your patient?
YES