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Curs 2 CB Metodologia Cercetarii Mar 2010

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    Corin Badiu, 2007

    Metodologia cercetrii tiinifice

    Ipoteza de lucruOrganizarea studiului

    Tipuri de studii

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    Obiective

    Dobandirea abilitatilor de cercetare

    Redactarea unui protocol de 10 pagini

    pentru un studiu realAnaliza altor studii (peer review)

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    Tipuri de Studii

    Nu sunt cea mai buna alegere pentru acest curs

    Studii fundamentale: molecule, celule, soareci

    Cost-eficienta, meta-analize

    Cercetare calitativa

    Ideal

    Un studiu observational (sau experiment) ce

    implica pacienti

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    Sectiuni ale protocolului de studiu

    Ipoteza de lucru

    Semnificatia (fondul)

    Designul studiului

    Populatia de studiu si recoltarea datelor;

    controlul de calitate al datelor

    Variabile si masuratori Analiza statistica a datelor

    Etica cercetarii medicale

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    Ipoteza de lucru

    Toate studiile incep cu o problema, intrebare

    fara raspuns

    Scopul este alegerea unei intrebari de

    cercetare relevante, ce poate fi transformata in

    proiect

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    Problema studiului

    Format pentru un studiu descriptiv

    Intr-o populatie de [populatie de studiu],

    care este prevalenta (sau media, mediana,etc.) [variabila dependenta]?

    Majoritatea studiilor au mai mult decat o

    problema de evaluat si rezolvat Protocolul de cercetare deriva din

    problema studiului

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    Format uzual (studii analitice):

    Intr-o populatie de [populatie de studiu],exista o asociere intre [variabiladependenta] cu [variabila independenta]?

    Problema studiului

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    Identificati problema studiului

    enuntata in rezumat

    Acute respiratory tract infections caused byStreptococcus pneumoniaeare a leading cause ofmorbidity and mortality in young children. We

    evaluated the efficacy of a 9-valent pneumococcalconjugate vaccine in a randomized, double-blindstudy in Soweto, South Africa. At 6, 10 and 14 weeksof age, 19,922 children received the 9-valentpneumococcal polysaccharide vaccine conjugated toa noncatalytic cross-reacting mutant of diphtheriatoxin (CRM197), and 19,914 received placebo

    Klugman KP, Madhi SA, Huebner RE, et al. A trial of 9-valent pneumococcalconjugate vaccine in children with and without HIV infection.

    N Engl J Med 2003; 349:1341-8.

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    In a population ofSouth African infantsis

    immunization with a 9-valent pneumococcal

    conjugate vaccineassociated with invasivepneumococcal disease?

    Intr-o populatie de [populatie de studiu], exista o asociereintre [variabila dependenta] si [variabila independenta]?

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    Originile unei probleme de cercetare

    Cercetarea literaturii

    Discutia problemelor din literatura

    A fi deschis la idei si tehnici noi

    Importanta invatarii

    Imaginatia

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    Caracteristicile unui studiu

    FINER Fezabil

    Interesant pentru investigator

    Nou

    Etic

    Relevant

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    CaracteristicileFINER

    Criterii de fezabilitate

    Numar adecvat de subiecti

    Expertiza technica adecvata

    Realizabil ca resurse de timp si bani

    Resurse umane calificate adecvat

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    CaracteristicileFINER

    Criterii de interes

    Studii cu impact populational

    Detalierea a noi mecanisme de boala

    Studii de eficienta terapeutica pentru

    metode noi

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    CaracteristicileFINER

    Criterii de noutate Confirma sau anuleaza cercetari anterioare

    Extinde cercetari anterioare

    Furnizeaza noi date

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    Consimtamant informat !!!

    Protejeaza pacientii sau NU ii expune unui riscsuplimentar

    Excluderea imediata / oprirea studiului in cazulunor efecte adverse severe

    CaracteristicileFINER

    Criterii de etica

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    Pentru cunoasterea stiintifica

    Pentru clinicieni, sanatatea publica sau

    politicile de sanatate

    Pentru directii de cercetare viitoare

    CaracteristicileFINERCriterii de relevanta

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    Probleme si solutii:

    Planul nu este FINER

    Nefezabil

    Prea larg

    Prea putini pacienti disponibili Metode sofisticate, peste abilitatile

    dovedite de investigator

    Prea scump

    Fara interes, noutate sau relevanta

    Evaluare etica inadecvata

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    Probleme si solutii:Planul nu este fezabil

    Prea larg

    Un set mai mic de variabile

    Se delimiteaza mai mult domeniul Insuficienti subiecti disponibili

    Extinde criteriile de includere

    Schimba criteriile de excludere

    Adauga alte surse de subiecti

    Extinde durata de inrolare

    Foloseste strategii de scadere a lotului

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    Metode in afara abilitatilor investigatorului Colaborare cu colegi cu aptitudini

    Consultarea de experti si reluarea literaturii pentru

    metode alternative Invata si practica aptutidinile cerute de studiu

    Prea scump Scade costurile designului de studiu

    Mai putini subiecti si masuratori

    Detaliu mai mic al masuratorii

    Mai putine vizite de urmarire

    Probleme si solutii:

    Planul nu este fezabil

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    Neinteresant, vechi sau irelevant

    Consulta mentorul

    Modifica problema cercetata

    Abordare etica nesigura

    Consulta comitetul de etica Modify the research question

    Probleme si solutii:

    Planul nu este FINER

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    Probleme and solutii

    Planul de studiu este vag

    Rescrie planul de cercetare mai amanuntit

    Detaliaza din planul de studiu Cum vor fi selectati subiectii si lotul martor

    Cum vor fi masurate variabilele

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    Probleme si solutii: exemple

    Ce relatie exista intre depresie si

    sanatate?

    Consumul de carne rosie determinacancer?

    Scaderea colesterolului seric previne

    boala cadiaca ischemica?

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    Anatomia Cercetarii Clinice

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    Fiziologia cercetarii clinice:

    Cum are loc?

    Se folosesc masuratorile intr-o proba /

    esantion /lot de studiu

    pentru a extrage inferente despre

    fenomene (variabile) intr-o populatie

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    Predictor* Rezultat

    Variabile de

    confuzie*

    Modificatori ai efectului*

    Tipuri de variabile

    *Considerate general ca expunere la factori de risc

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    Problema de studiu

    In studii descriptive:

    Intr-o populatie de [study population], careeste prevalenta [outcome variable]?

    In studii analitice:

    Intr-o populatie de [study population], este[predictor variable]asociata cu [outcomevariable]?

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    Tipuri de studii clinice

    Studii fara variabile

    Studii de caz, serii de cazuri, editoriale,

    opinii / comentarii, rapoarte review Studii cu o singura variabila

    Studii descriptive

    Studii cu 2 variabile

    Experimente

    Studii observationale

    Meta-analize si review-uri sistematice

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    Ierarhia tipurilor de studii clinice

    Descriptive studies

    Experimental studies

    Cohort Case-control Cross-sectional

    Observational studies

    Analytic studies

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    Variabila predictor(independenta)

    Variabila rezultat(dependenta)

    Variabile

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    An important methodology question which isimplicitly related to study objectives.

    Imperative to decide on the study design beforedata collection and analysis

    Study Design is important because it serves the

    primary purpose of maximizing study validity, inparticular minimizing biases.

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    What study designs have you

    come across? Various designs differ in their

    vulnerability to threats to study validity,

    a strong design being less vulnerablethan weaker designs.

    However, strength tends to trade offwith cost. Stronger design is generally

    more costly to do.

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    Factors influencing selection of studydesign

    1. Objective of the study- research

    questions

    2. Occurrence of disease / exposure

    -rare/ common

    3. Ethical issues

    4. Resources- money, manpower, machine

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    What study design is mostappropriate?

    Do cell phones cause brain cancer?

    Does diet affect breast cancer risk?

    Does passive smoking cause lung

    cancer?

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    Classifications of research

    design

    1. Experimental/ Quasi-experimental or

    observational

    2. Directionality of the study in relation to

    exposure and disease occurrence

    3. Quantitative /qualitative

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    Hulleys Research Question

    (1993)

    Ar trebui sa primeasca substitutie cu estrogeni

    femeile postmenopauza?

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    Hulleys Research Question (1993)

    Subiecti: femei postmenopauza

    Predictor: estrogeniRezultat: ?

    Ar trebui sa primeasca substitutie cu estrogeni

    femeile postmenopauza?

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    Ameliorarea problemei de cercetare

    Tratamentul cu estrogeni previne

    accidentul coronarian la femei postmenopauza?

    Subiecti: femei postmenopauza

    Predictor: tratament cu estrogeni vs no treat

    Rezultat: accident coronarian

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    FINER?

    Fezabil

    InteresantNou

    Etic

    Relevant

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    Seven basic study designs :

    1. Randomized controlled trial

    2. Cohort study

    3. Case-control study4. Sample survey or cross sectional

    study

    5. Ecologic or trend study6. Case report or series

    7. Qualitative research

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    Ncesitatea desing-ului

    Trial clinic randomizat

    Puncte finale

    Interes primar

    Studiu observational

    Cross-sectional

    Case control

    Cohorta

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    1.Experimental/Interventional Studies-

    Randomized controlled trial

    Evaluate new forms of therapy and prevention

    New drugs and other treatment of disease

    New medical and health care technology

    New methods of primary prevention

    New programs for screening and early detection of

    disease

    New ways of organizing and delivering health services

    ( community trial )

    Impact of new policies in health care and health care

    financing ( community trial )

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    Randomized controlled trial

    Strongest design- randomization,minimize selection bias ( but not

    completely) Not ethical- harmful intervention, poor

    clinical outcome

    Not practical- rare disease, rareoutcome

    Study subjects participation is crucial

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    Randomized Controlled Trial

    Elements Design

    Randomization

    New treatmentCurrent treatment

    /no treatment

    Defined population

    ImprovedNot

    improved ImprovedNot

    improved

    Intervention

    Outcome

    Selection of subjects-similar features

    -inclusion/exclusion criteria

    Allocation ofsubjects

    Data collection

    Masking (blinding)

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    RCT

    Blinding Double- subjects & investigators

    Single subjects (placebo effect)

    Triple blind- subjects & investigators & statisticians

    Outcome/endpoint improvement ( desired effect) and side effects

    must be explicitly defined

    measured comparably in all study groups

    Multi-centre trial

    Comply with GCP requirements Clinical trials/ community trials

    Results of RCT- benchmark- good clinical practice (GCP) ,clinical governance, treatment protocol.

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    Types of RCT: Superiority or equivalence trials A

    Parallel-most common B Cross over

    - Plannedwashout

    period

    A B

    B A

    - Unplanned

    Surgical Medicalrandomized

    randomized

    Refuse surgery Require surgery

    Analyze outcome by intention to Rx No surgerySurgery

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    Limitation

    1. ? effective in uncontrolled community

    2. consent refusal- automatic selection

    ( people who participate are different from those whodo not)

    3. Non compliance ( people who are compliant arevery different from those who are not)

    - drop-outs: no adherence to experimentalregimen, loss to f/u

    -drops-in: no adherence to control regimen

    4. Compliance -Need monitoring

    5. Most costly

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    Observational studies

    1. Cohort study

    2. Case-control study3. Cross sectional study

    4. Ecologic or trend study

    5. Case report or series6. Qualitative research

    Direction, timing , +/- control

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    Studiu de cohorta

    Subiecti

    5000 femei cu varsta 55+ ani

    Factor predictor: estrogeni post-menopausal?

    Outcome:

    Incidenta accidentelor coronariene dupa 5-ani de terapie

    W ?

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    When is a cohort study warranted ?

    When there is good evidence of anassociation of the disease with a certainexposure

    When exposure is rare and incidence ofdisease among exposed is frequent

    When the time between exposure and

    disease is short When the investigator has a long life

    expectancy!

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    Definition

    Cohort: any designated group of

    individuals who are followed or traced

    over a period of time Free of the outcome at the beginning of

    follow-up (population at risk)

    Usually defined or divided by exposurestatus

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    Population at Risk

    All subjects within a cohort must be free

    of the outcome at the start of the follow-

    up period All subjects must be at risk for

    developing the disease (population at

    risk)

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    Outcome Measure

    Closed Cohort

    Incidence Rate

    Incidence Proportion (Risk) provided there is limited impact due to

    competing risk and loss to follow-up

    Open Cohort Incidence Rate

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    Merits of Prospective VS.Restrospective Cohort Studies

    Prospective

    Cohort Study Better control of the

    quality and quantity of

    the data

    less potential for bias

    More time consuming

    More expensive

    Retrosepective

    Cohort Study Poorer control of the

    quality and quantity of

    the data

    greater potential forbias

    Less time consuming

    Less expensive

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    Loss to Follow-up

    Problem, especially if lost subjects are

    at higher/lower risk for developing the

    outcome compared to other subjects even worse if this problems is different with

    comparison groups

    < 60% follow-up is generally regardedwith skepticism

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    Analysis of data-cohort study

    Start with exposure h/o, then follow to see

    whetherDisease +

    Exposed +

    Exposed -

    Disease - totalIncidence rate

    of disease

    a b

    c d

    a+b

    c+d

    a/a+b

    c/c+d

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    Analysis of data-cohort study(cont)

    Absolute risk= incidence of disease cases

    in exposed group/total population

    Relative risk= incidence of dis among E+

    incidence of dis among E-

    Odd ratio = ad/bc

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    Limitations

    Some exposure can change over time e.g. aging, life style (diet, smoking pattern), exposure to pharmaceutical agents,air pollution

    Changes on method over time- disease identification

    Prospective - follow-up, thus long period Costly

    Potential bias selection bias ( who has been exposed and who has not )

    information bias historical data

    bias in outcome assessment

    non-response and loss to f/u

    analytical bias

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    Cross-sectional design

    Subiecti

    2000 femei varsta 55+ ani

    Predictor:

    Tratament post-menopausal cu estrogeni?

    Rezultat:

    Istoric de accident coronarian?

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    Sample survey or cross sectional study :

    It is a survey of the frequency of disease and

    other characteristics in a defined population

    at one particular time.

    Focus on describing a state or process at a

    fixed time.

    Suitable for describing prevalence anddistribution of heath problem in a community.

    (prevalence or health survey).

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    Sample survey or cross sectional study : - cont

    In clinical research, used in :

    Describing disease presentation (spectral description

    study)

    Diagnostic test accuracy study

    Quality of care assessment.

    Generally efficient but large scale community

    survey can be expensive. Sometimes survey data given causal

    interpretation (pseudo-longitudinal) but liable to

    error, caution.

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    Advantages of Cross Sectional

    Study Design One stop shopping

    Less expensive

    Potentially can detect effect of exposurethat do not vary over time

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    Disadvantages of Cross

    Sectional Study Design May not detect associations that for

    diseases with short duration that have

    cyclic or seasonal trends (e.g. someinfectious diseases)

    May require over-sampling of low

    prevalence exposure or disease groups

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    Design Case-control

    Subiecti / femei la menopauza

    Cazuri: 100 femei cu accident coronarian

    Controale: 100 femei fara patologie cardiaca

    Predictor:

    Au luat estrogeni post-menopauza?

    Rezultate:

    Cazuri vs controale

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    Controls

    Case Control Studies compareexposure history of cases and controls

    Controls provide exposure distributionof exposure (exposed and unexposedcohorts) in source population that gaverise to the cases in the study

    Biggest Problem: Identifying anappropriate control group

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    Sources for Controls

    Population Controls

    Neighborhood Controls

    Random-Digit Dialing

    Hospital-Based Controls

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    Nested Case Control Studies

    Every Case Control Study can be thought as

    being conducted within a cohort study

    Cases represent the outcomes of the cohort

    Controls provide estimate of exposure distribution

    of cohort

    Traditionally, Nested Case Control Study

    usually refers to study that are conductedwithin the experience of a well-defined cohort

    study

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    2x2 Table

    Case Control

    Exposure + a b

    Exposure - c d

    Total M1 M0

    OR = (a/c) / (b/d)

    (a/c) / (K1/K0)

    IRR

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    Hospital-Based Controls

    Most appropriate for hospital-based

    cases with ill-defined catchment area as

    source population Often chosen from diagnostic groups

    not thought to be related to the

    exposure better to choose more than one diagnostic

    group for controls

    minimizes impact of a poor choice

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    Hospital-Based Controls

    History of diagnosis for different

    condition related to exposure is not

    grounds for exclusion Some cases may have the same history

    Assumption:

    catchment area for control diagnosis issame as catchment area for cases

    control reflect exposure distribution for

    source population of cases

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    Comparison of Case Control

    and Cohort Studies Primary Difference:

    Cohort Study involved complete

    enumeration of the source population Case Control Study involved a sample

    (controls) of the source population

    Case Control Studies are modified Cohort

    Studies

    Wh i t l t d

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    When there is good evidence of anassociation between a certain exposureand the disease

    When disease is rare and exposure isfrequent among exposed

    Advantage:

    Cost- relatively inexpensive

    Sample sizerelatively small

    When is a case control study

    warranted?

    A l i f d t

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    Analysis of data-case control study

    Begin with cases with disease and controls without

    disease, then measure past exposureDisease +

    Exposed +

    Exposed -

    Disease - total

    a b

    c d

    a+b

    c+d

    Odd ratio= a/a+c / b/b+d= ad/bc

    Proportion of

    exposeda/a+c b/b+d

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    Limitation

    Selection of appropriate controls

    Recall bias

    - Human ability to recall

    - Recall bias (Case may remember their

    exposure more than controls do)

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    Etic?

    Echivalenta (nu este sigur daca dominabeneficii sau riscuri)

    Beneficii ale terapiei de substitutie

    Scad simpotomele de climax ? Preventia fracturilor ? Preventia BCI ? Preventia Alzheimer

    ? Cresterea calitatii vietii

    Riscuri

    ? trombo-embolism pulmonar

    ? Cancer mamar

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    Relevant?

    Estrogeni / estroprogestative

    Decizia afecteaza o mare parte din

    populatie

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    TRECUT PREZENT

    Cazuri

    Controale

    Yes

    Yes

    No

    No

    Cancer mamar

    Fara cancer de san

    A primit HRT?

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    Case report or series :

    Description of one or several cases in

    which no attempt is made to answer

    specific hypotheses or to compareresults with another group of cases.

    classical clinical study; its value probably

    under rated (Pickering Lancet 19##)

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    Case report or series

    Description of one or several cases in which

    no attempt is made to answer specific

    hypotheses or to compare results with

    another group of cases

    No control

    Classical clinical study

    Its value probably under rated

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    Case Reports and Case Series

    Example: investigators at a single institution

    note that a small number of patients treated

    with a alternative (complementary) therapy exhibit

    longer survival and better survival than "expected"

    Example: investigators notice a higher than expected

    incidence of a cancer in a community

    Example: investigators note a common occupational

    exposure in a series of patients with a rare cancer

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    Case Reports and Case Series

    Problems: lack of a control group

    no measure of effect

    no formal statistical analysis

    Advantages: hypothesesgenerators

    C S i With Lit t

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    Case Series With LiteratureControls

    Compare outcomes of case series to

    "expected" results based on existing

    records (e.g. published results, nationalincidence/mortality rates)

    Problems: lack of comparability

    Confounding Healthy Worker Effect

    Bias

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    5. Ecologic or trend study :

    Group based study

    Unit of observation is a group egcountry, state etc.

    Observed effect difficult to interpret at

    individual level (ecologic fallacy). Otherwise efficient to do.

    5. Ecologic or trend study :

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    5. Ecologic or trend study :

    Group based study, unit of observation is a

    group e.g. country, state etc.

    Ignore variability between individuals

    May ascribe to members characteristics they donot possess as individuals

    Quantity of salt sold at

    Henan province in China

    Age standardized

    death rate per 1000

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    Qualitative research :

    Development of concepts which help us to

    understand social phenomena in natural

    settings, giving due emphasis to the

    meanings, experiences, and views of all theparticipants

    It does not primarily seek to provide

    quantified answers to research questions

    Particularly useful for explaining complex

    phenomena not amenable to quantitative

    research

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    Qualitative research : - cont

    It has an important role in medical research

    because health care deals with people and

    people are more complex than the subjects of

    the natural sciences.

    There is a whole set of questions about

    human interaction that we need answers to.

    Obvious areas of application are doctor-patient relationship, treatment compliance,

    clinical decision making process, issues on

    health service organisation and policy issues.

    Qualitative research-contd:

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    Qualitative research cont d:

    Development of concepts which help us to understandsocial phenomena in natural settings, giving due emphasisto the meanings, experiences, and views of all theparticipants

    Useful for explaining complex phenomena not amenable toquantitative research

    Approaches- Focus group, observation, interview, diary

    Obvious areas of application are doctor-patient relationship,treatment compliance, clinical decision making process,issues on health service organization and policy issues

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    Conceptia unui plan de cercetare

    1. Definitia problemei

    2. Dezvoltarea planului de cercetare

    Lista elementelor studiului Identificarea referintelor publicate

    3. Introducerea (fondul problemei) sisemnificatia sa (istoric al cercetarilor

    anterioare, motivatie, importanta)

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    Plan de studiu

    Problema cercetata

    Semnificatie (background)

    Designul studiului

    Populatia de studiu si

    esantionarea Variabile si masuratori

    Elemente statistice

    Aspecte etice

    Controlul calitatii sievaluarea datelor

    Problema principala a studiului?

    De ce este important?

    Cum se va face studiul ?

    Care sunt subiectii si cum suntselectati?

    Ce masuri vor fi luate?

    Dimensiunea lotului si analiza?

    Exista probleme etice?

    Cum se asigura controlul calitatiidatelor si analizei acestora?

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    Fond si semnificatie

    Bazat pe experienta

    Atentie la idei noi

    Atentie la tehnologii noi Sa fim constienti despre punctele forte si slabe ale

    cercetarilor anterioare similare, proprii sau de

    literatura

    Sa stim ce dorim sa comunicam / confirmam la final

    Fondul si semnificatia problemei /

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    Fondul si semnificatia problemei /

    importanta pentru protocol

    Asemanator cu introducerea la un articol

    Introduce cercetarea propusa, in context

    Descrie motivatia studiului

    Ce se stie despre topic

    De ce este problema propusa, importanta?

    Ce tip de raspuns asteptam de la studiu?

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    Fond si semnificatie

    Citarea cercetarilor relevante anterioare (inclusiv

    propriile date)

    Indica punctele forte si slabe ale studiilor anterioare,

    ca si intrebarile ramase fara raspuns.

    Arata cum vor fi folosite rezultatele studiului propuspentru rezolvarea neclaritatilor si influentarea politicii

    de sanatate sau practicii clinice

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    Gasirea literaturii adecvate

    End note, Reference manager

    Verifica formatul referintelor conform

    instructiunilor pentru autori si sunt incluse pe

    masura ce se scrie protocolul

    Se pastreaza copii ale tuturor referintelor

    PubMed: www.ncbi.nlm.nih.gov

    Comunicari personale (cine si cand)

    Date nepublicate (Cel mai bine se evita)

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    Gasirea literaturii adecvate

    End note, Reference manager

    Verifica formatul referintelor conform

    instructiunilor pentru autori si sunt incluse pe

    masura ce se scrie protocolul

    Se pastreaza copii ale tuturor referintelor

    PubMed: www.ncbi.nlm.nih.gov

    Comunicari personale (cine si cand)

    Date nepublicate (Cel mai bine se evita)

    Fundamentele Stiintifice ale Cercetarii

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    Fundamentele Stiintifice ale Cercetarii

    mai multe principiifundamentale sunt utilizate in

    cercetarea stiintifica:

    1.Ordinea

    2.Deductia si Sansa

    3.Evaluarea si Probabilitatea4.Ipoteza

    Fundamentele Stiintifice ale Cercetarii

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    Fundamentele Stiintifice ale Cercetarii

    Evaluarea si Probabilitatea(1)

    Cerinta critica a efectuarii

    proiectului in cercetare, aceea

    care asigura validitatea, este

    evaluarea probabilitatii de la

    inceput pana la capat

    Fundamentele Stiintifice ale Cercetarii

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    Fundamentele Stiintifice ale Cercetarii

    Ipoteza ipotezele sunt afirmatii atent construite referitoare la un fenomen

    intalnit intr-o populatie

    ipotezele pot fi generate fie prin:

    rationament deductiv

    rationament inductiv rezultat din observatii anterioare

    Concluzii

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    Concluzii

    Les sciences sont faites par additions.

    Nul ne commence ou acheve.

    Nous sommes montes sur les epaules dun geant. Nous

    voyons tot ce que voit le geant, et quelque chosedavantage.

    Guy de Chauliac, 1684


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