Penelitian Kilinis (Etiologi)

8/12/2019 Penelitian Kilinis (Etiologi)

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CLINICAL RESEARCHETIOLOGYProf.Dr.dr . Rusdi Lamsudin, M .Med.SC, SpS(K)

Clinical Epidemiology & Biostatistics Unit/

Department of Neurology

Fakulty of Medicine

Gadjah Mada university


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Inference cause effectrelationship

Coffee drinking & MI

Hypertension & Stroke Smoking cigarettee & Stroke

Eating satae kambing & Hypertension


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Coffee drinking & MI

Explanation Type of assoc Basic for assoc Whats really

going on in the

population

1. Chance Spurious Random error Not related

2. Bias Spurious Systmatic error Not related

3. Effect-cause Real Cart before the horse MI is a cause of Coffee

drinking

4. Effect-effect Real Counfounding Coffee dringking & MI

caused by a third,extrinsic factor

5. Cause-effect Real Cause and effect Coffee drinking is a

cause of MI


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Designing for Etiologic Study

Experiments

Cohort

Cross-sectional

Case-control


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Cohort StudyPrimary purposes

Descriptive - Incidence Analytic - analyze associations between

risk factors and those outcomes


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Cohort Studies

Prospective cohort studies

Retrospective cohort studies

Nested case-control studies Double-cohort studies and external

controls


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Prospective cohort design

Risk factor

presentRisk factor

absent

Disease No disease

Disease No disease

Population

Sample

THE PRESENT THE FUTURE


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Porspective Cohort Design

Strengths

Powerful strategy for defining the

incidence and investigating the potential

causes of a condition

The time sequence strengthens the

inference that factor may be a cause of theoutcome


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Strengths (Cont)

Gives the investigator an opportunity to

measure important variables completelyand accurately

Especially valuable for studying theantecedents of fatal diseases


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Weaknesses

Expensive

ineffeicient Cannot be used for studying rare diseases

Need large number of subjects for long

periods of time


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Retrospective cohort design

Risk factor

presentRisk factor

absent

Disease No disease

Disease No disease

Population

Sample

THE PAST THE PRESENT


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Retrospective cohort designStrengths

Can establish that predictors variables

preceded the uotcomes

Guarantee that measurement of predictors

variables was not biased

much less costly and time-consuming thatprospectives ones


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Retrospective cohort designStrengths(Cont)

The subjects are already assembled,

baseline measurements have already been

made and the follow-up period has already

taken place.

All subjects who developed the outcome of

the subjects who developed the outcome

(cases) and all those did not (controls)

come from the same population


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Retrospective cohort designWeaknesses

Investigator has no control over the nature

and the quality of the measurements that

were made

The existing data may not include

information that is important to answeringthe research question


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Nested case-control design

Disease present

Disease absent

Risk factor

present

Risk factor

absent

Risk factor

present

Risk factor

absent

THE PRESENT

MEASUREMENT IN

PRESENT; SPECIMENT

FROM THE PAST

Study cohort

Population

All

cases

Sample

of

control


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Prospective double-cohort design

Risk factor

present

Risk factorabsent Disease No disease

Disease No disease

THE PRESENT THE FUTURE

Pop #1

Pop #2

Sample (cohort #1

Sample cohort #2


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STEPS IN PLANNING

A COHORT STUDY When to use a cohort design

Choosing among cohort designs

Selecting subjects Measuring predictor and confounding

variables

Following subjects and measuringoutcomes

Analysing incidence and RR


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Cross-sectional design

Risk factor;

Disease

Risk factor;

No disease

No risk factor;

Disese

No risk factor;

NO disease

THE PRESENT

Population

Sample


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(Strengths)

No waiting to see who will get the disease

fast and inexpensive

no problem with loss of follow-up

the only one to give the prevalence of

disease or risk factor

convenient for examining networks of

causal links


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(Weaknesses)

Difficult to establish causal relationship

Impractical for the study if the design

involving collecting data on a sample of

individuals from the general population


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Case-control design

Disease

Risk factor

absent

Risk factor

present

Risk factor

absent

Risk factor

presentNo disease

THE PAST OR PRESENT

THE PRESENT

Sample

of cases

Sample

of

control

Pop

withdisease

(cases)

Pop

without

disease

(control


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Case-control design

(strengths) Well suited to study of rare diseases or these with long

latency

Relative quiks to mount and conduct

Relative inexpensive

Requires comparatively few subjects

Existing records can occasionally be used

No risk to subjects Allows study of multiple potential causes of disease


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Case-control design

(weaknesses) Relies on recall or records for information on past

exposure

Validation of information is difficult or sometimes

impossible

Control extranous variables may be incompleted

Selection of appropriate comparison group my be difficult

Rates of disesase in exposed and unexposed individuals

cannot be determined

Methods relatively unfamiliar to medical community and

difficult to explain

Detailed study of mechanism is rarely possible


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Step-by-step of planning and

conducting of case-control study Developing and stating the background of the study

Stating the research question

Stating the hypotheses

Clearly defining the disease under study and exposure of

interest

Selecting the cases

Defining and selecting a control group developing and testing research instruments

Conducting field operations

Planning the statistical analysis

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