Journal Club (méthodologie) Introduction à la lecture d’articles médicaux (Partie 3)  

Journal Club (méthodologie) Introduction à la lecture d’articles médicaux (Partie 3)
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Introduction à la lecture d’articles médicaux (3)
Dr. Ioannis KOKKINAKIS
Chef de Clinique
Service de Médecine Interne - Hôpital du Valais Sion
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29.08.2017

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Qu’est
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1.
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7.
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-ce qu’on a déjà vu?
Grille de Lecture pour ERC
Autres Grilles des Lecture
Recommandations Int.
Types d’études
Etudes observationnels
Etudes expérimentales
Métanalyses
Lien pour télécharger les présentations:
https://www.dropbox.com/sh/
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?dl=0

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Qu’est-ce qu’on va voir …
Rappel courte de la grille de lecture
PICOTS
Consort Statement
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Rappels statistiques de base

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Rev Mal Resp 2002, 19, 505-514

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Rev Mal Resp 2002, 19, 505-514

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Notre Grille de Lecture (SSMI)

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Autres Grilles de Lecture

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https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3380258/

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fiabilit
http://
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Guidelines internationaux?
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Consolidated Standards of Reporting Trials
– Premì re version en 1996 rédigée par le Groupe CONSORT, un panel
d’experts en méthodologie des essais cliniques
Dernière version 2010
Objectifs du CONSORT
Standardiser le contenu des articles traitant des essais thérapeutiques
randomisés en groupes parall̀ les
Permettre une lecture critique des articles publiés: évaluer la
et la pertinence des résultats (validités interne et externe)
– Améliorer la thodologie des essais cliniques
www.consort-statement.org
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é

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http://www.consort-statement.org

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CONSORT 2010 checklist
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http://www.consort-statement.org

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http://www.consort-statement.org

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Research Question Title
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P
Population
I
Intervention of interest
C
Comparator / Control
O
Outcomes of interest / Observation
T
Time
S
Study type - Randomised controlled trial
Effects of radiotherapy with concomitant and adjuvant
temozolomide versus radiotherapy alone on survival in
glioblastoma in a randomised phase III study: 5-year analysis of
the EORTC-NCIC trial
Stupp, Roger et al. The Lancet Oncology , Volume 10 , Issue 5 , 459 466

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Quelques rappels statistiques

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Incidence
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Prévalence
Mortalité
Récurrence

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Sensibilité
Sensitivité
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Valeur prédictive positive
Valeur prédictive négative

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COMPAS 2eme édition, CORNUZ Jacques, Pasche Olivier, 04.2014
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Sensibilité
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Sensitivité
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Valeur prédictive positive
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Valeur prédictive négative

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A retenir: Test sensible = peu de faux négatifs
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Test spécifique = peu de faux positifs
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COMPAS 2eme édition, CORNUZ Jacques, Pasche Olivier, 04.2014

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Courbe
ROC
(
reciever
operating
characteristics
)
.
La courbe ROC (receiver operating characteristics) informe sur le rendement d’un test
Elle met en relation le taux de vrais-positifs (sensibilité) avec celui des faux-positifs
(1 spécificité).
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COMPAS 2eme édition, CORNUZ Jacques, Pasche Olivier, 04.2014

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Courbe ROC pour BNP
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COMPAS 2eme édition, CORNUZ Jacques, Pasche Olivier, 04.2014

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COMPAS 2eme édition, CORNUZ Jacques, Pasche Olivier, 04.2014

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Rapports de vraisemblance (RV)
(likelihood ratio)
- Il exprime combien de fois le résultat obtenu est plus fréquent chez
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A retenir:
Les RV permettent de calculer la probabilité d’une maladie apr̀ s
avoir réalisé un test.
Ne varient pas en fonction de la prévalence de la maladie dans la
population dont est issu le patient.
Un test est utile lorsque son RV positif est > 5
COMPAS 2eme édition, CORNUZ Jacques, Pasche Olivier, 04.2014

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COMPAS 2eme édition, CORNUZ Jacques, Pasche Olivier, 04.2014

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COMPAS 2eme édition, CORNUZ Jacques, Pasche Olivier, 04.2014

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Null hypothesis?
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Suppose a trial is undertaken to investigate the superiority of one treatment over
another in terms of some outcome of interest (e.g. mortality).
Null hypothesis : in truth, there is no difference between the treatments in their impact
on that outcome, i.e. that the treatments have the same effect.
Alternative hypothesis?
Primary endpoint?
Secondary endpoint?

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Taille de l’échantillon d’une étude RCT

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Précision de l’estimation de l’effet du traitement?
A trial needs to be Large
Patients vary considerably in their
response to treatment. In order to
obtain a precise estimate of any
treatment effect, sufficiently large
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numbers are require

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Calculer la taille de l’échantillon
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Ou plus simplement STATA vs SPSS

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Est-ce que la taille de l’échantillon doit être ajusté?

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p-value
the probability (ranging from 0 to 1) that the results observed in a trial (or
results more extreme) could have occurred by chance if the null hypothesis is
true.
The smaller the p-value, the less likely the null hypothesis is to be true.
p-value=0.0001 indicates the null hypothesis is very unlikely to be true whereas
p-value=0.53 indicates the observed results could easily have arisen by chance
Confidence interval
A confidence interval is an interval, constructed around an estimate from a sample (e.g. the
estimate of the size of effect of an intervention), that indicates the uncertainty in the
estimate because it was obtained from a sample.
If independent samples are taken repeatedly from the same population, and a confidence
interval calculated for each sample, then for example 95% (the confidence level) of the
intervals will include the unknown population parameter 95% of the time.
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Confidence intervals can be for other values e.g. 90%, 99%, 99.9%.

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L’étude a été arreté precocement … pourquoi?
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Consider the reasons why you might want to stop a
trial early...
treatment effects which require action.
Interim analysis might indicate the new treatment under
investigation to be:
sufficiently superior than the comparison treatment to warrant stopping
inferior to the comparison treatment and therefore compromising the safety
of patients on the new treatment
Other reasons include stopping because the trial results are unlikely to be
conclusive in favour of the new treatment, poor patient recruitment or other
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administrative issues.

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NNT
need
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Number needed to treat
The Number Needed to Treat (NNT) is the number of patients you
to prevent one additional bad outcome (death, stroke, etc.).
NNT = the inverse of the Absolute Risk Reduction (ARR) :
NNT = 1/ARR
Where ARR = CER (Control Event Rate) EER (Experimental Event Rate).
Your drug reduces the risk of a bad outcome from 50% to 30%
ARR = CER EER = 0.5 0.3 = 0.2, donc 20 %
therefore
NNT = 1/ARR = 1/0.2 = 5
to treat
.

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Nicholas J. Schork Nature vol 520, p 609, April 2015

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Biais

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Forest plot

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Merci pour votre attention

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Further reading
http://www.nejm.org/page/clinical-trials-series

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Sensitivity / Specificity
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