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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