STUDY DESIGNS for Adilabad

8/7/2019 STUDY DESIGNS for Adilabad

http://slidepdf.com/reader/full/study-designs-for-adilabad 1/43

STUDY DESIGNSSTUDY DESIGNSDr.J.V.DixitDr.J.V.Dixit

MD(PSM),DHA,DHRM,FISCDMD(PSM),DHA,DHRM,FISCD

Associate Professor,Associate Professor,

PSM Department,PSM Department,

Government Medical College,Government Medical College,

Aurangabad.Aurangabad.

[email protected]@rediffmail.com



Research:

Ground reality?!



Types of scientific studiesTypes of scientific studies

� Non experimental

(Observational

studies)

� Investigator has no

control over major

independent or

predictor variables

� Existing phenomenon

used

� Experimental studies

� Investigator has

control over major

independent and

predictor variables

� Study tests the effect

of intervention oncertain aspect of

health or disease



Purpose of scientific studiesPurpose of scientific studies

� Community diagnosis

� Planning and evaluation

� Evaluation of individual¶s risks and chances

� Search for causes and risk factors

� Study of natural history of disease

� Syndrome identification

� Examining clinical decision making� Assessing health status of community

� Evaluation of utility of a treatment



General principles in designingGeneral principles in designing

studies relate with«studies relate with«

� Study characteristics: Type of studydesign to be used and way in which studywill be conducted

� Merits and demerits of that study design

� Methodology: Methods of data collection,selection of subjects and data analysis

� Other issues: Ethical problems, limitationsof study, resources available, costs andrisks associated with study



Criteria for good study designCriteria for good study design

� Objectivity : Methods used for collection of data

and scoring of responses should be objective

� Reliability : It is the consistency throughout a

series of measurements

� Validity : The method/equipment should

measure what it is supposed to measure

� Generalisability : Should provide informationregarding generalisability of the findings of the

present study to parent population



Types of study designsTypes of study designs

� Explorative : emphasis on discovery of ideasand insights. Also called as formulative designs

� Descriptive : Characteristics of an individual, a

group or situation are described� Diagnostic : Determines frequency with which

something occurs or its association withsomething else

� Experimental : These designs try to find out thecausal influence of one variable on another variable



Some study designsSome study designs

1) Case report : Brief, objective report of

clinical characteristic or outcome from a

single clinical subject or event

� It is the first evidence of an unexpected or

unusual event

� Results are rarely generalizable



Some study designs (Cont«)Some study designs (Cont«)

2) Case report series : Objective and brief

report of a clinical characteristic or

outcome from a group of clinical subjects.

� Problems in generalization due to ± biased

selection or un representative ness of

subjects, lack of control group




3) Incidence - Prevalence studies : Type of case series report« Entire population welldefined and surveyed regarding

parameters in question� Rates useful to compare populations

obtained

� Rates of little use in rare events

� Sampling procedure if not random affectsutility significantly




4) Case control study : Common first approach totest causal hypothesis

� Exposure and outcome have occurred beforestart of study

� Proceeds backwards from effect to cause� Uses control group to support or refute inference

� Basic steps : selection of cases and controls,matching, measurement of exposure and

analysis and interpretation� Odds ratio obtained



Case Control studyCase Control study

1) Selection of cases: Define case by usingdiagnostic criteria and eligibility criteria

Cases can be from hospitals or generalpopulation

Controls must be free from diseaseunder question

Can be obtained from hospital, relatives,neighborhood, general population

One control for one case; maximum 4



Case Control study (Cont«)Case Control study (Cont«)

� Confounding factors and role of matching

It is a factor that is one which is associated

with ³exposure´ but is itself a ³risk factor´for the disease

Alcohol--- esophageal cancer study

smoking is confounding factor

� Group and paired matching




Effect present Effect absent

Cause present a b

Cause absent c d

Total (a+c) (b+d)




� Exposure rates

Cases = a/(a+c)

Controls= b/(b+d)Odds Ratio= ad/bc

If it is 6, it means risk of getting disease in

exposed it 6 times than that of non exposed



JUST RELAX A

WHILE !




5) Cohort study : Used to obtain additionalevidence to support or refute a hypothesis

� Study goes from cause to effect

� Uses control cohort to support or refute

inference� Involves a period of observation or follow up

� Steps are: selection of study subjects, obtainingdata on exposure, selection of comparisongroup, follow up, analysis and interpretation

� Relative risk, attributable risk and populationattributable risk obtained



Cohort study (Cont«)Cohort study (Cont«)

� Cohort is defines as a group of people

who share a common characteristic or

exposure within a specified time period

� Cohort studies are indicated when there is

good evidence of association between

exposure and disease and when exposure

is rare but the incidence of disease inexposed is high




Effect

present

Effect

absent

Total

Causepresent

a b a+b

Cause

absent

c d c+d




� Relative risk = incidence among exposed/incidence in non exposed

� Attributable risk = (Incidence of diseaseamong exposed ± incidence among nonexposed)/ incidence rate among exposed

� Population attributable risk = Incidence of

disease in the total population ± incidenceof disease among those who are notexposed to cause




6) Randomized controlled trials : This is anexperimental study

� Like cohort study (except intervention)

� Faces additional problems of cost, ethics and

feasibility� Steps : Preparing a protocol, Selection of reference and experimental populations,Randomization, Intervention, Follow up,Assessment of outcome and analysis

� Analysis : Rates of measured outcomes arecompared



Difficult road ahead!



PurposePurpose

� To provide scientific proof of aetiological or

risk factors which may permit modification

or control of the disease

� To provide a method of measuring the

effectiveness and efficiency of health

services for the prevention, control and

treatment of disease and improve thehealth of the community



Population or sample from populationPopulation or sample from population

diagnostic test applieddiagnostic test applied

persons with disease persons wpersons with disease persons w

under study under study

persons willing persons nopersons willing persons no

RandomizationRandomization

persons receiving persons not receivpersons receiving persons not receiv

intervention under study intervention under studyintervention under study intervention under study

follow upfollow up

cured not curedcured not cured cured cured not cured

Fig : showing typical clinical trialFig : showing typical clinical trial



Basic stepsBasic steps

� Draw protocol

� Select reference and experimentalpopulation

� Make necessary exclusions

� Randomization

� Manipulation or intervention

� Follow up

� Assessment of outcome



Some study designsSome study designs

� Concurrent parallel study design: Patients

remain in the study group or control group for

the complete duration of the investigation

� Cross over type of study design: After taking

treatment the study and control groups are

taken off from the medication. Then two

groups are switched, those receivingtreatment receive placebo and controls

receive treatment



Types of RCTTypes of RCT

� Clinical trial

� Preventive trials

� Risk factor trials� Cessation experiments

� Trial of aetiological agents

� Evaluation of health services



Phases of clinical trialPhases of clinical trial

� Pharmaceutical clinical trials are commonlyclassified into four phases

� Phase I

Usually a small group(20-40)of healthyvolunteers selected.Includes trials designed to assessthe safety, tolerability, pharmacokinetics, andpharmacodynamics of a therapy

There are 2 specific kinds of phase I trials-SAD studies& MAD studies:single ascending dose ,multiple ascending dose




(Cont«)(Cont«)

� Phase II

Once the safety of therapy has been confirmed

in phase I trials, phase II trials are performed on

larger groups(200-300) and are designed toassess clinical efficacy of the therapy; as well as

to continue phase I assessments in a larger

group of volunteers and patients.

The development process for a new drugcommonly fails during phase II trials due to the

discovery of poor efficacy or toxic effects.




(Cont«)(Cont«)� Phase III

Phase III studies are randomized controlled trialson large patient groups (300-3000 or more) and areaimed at being the definitive assessment of the new

therapy. Once the drug has proven satisfactory over phase III trials, the trial results are usually combinedinto a large document containing a comprehensivedescription of the methods and results of humanand animal studies, manufacturing procedures,

formulation details, and shelf life. This µregulatorysubmission¶ information is provided for review tovarious regulatory authorities for marketingapproval.



An uphill task!




(Cont«)(Cont«)

� Phase IV :-Phase IV trials involve post-launch safety surveillance and ongoing technical support

of drug. It is designed to detect any rare or long term adverse effects over a muchlarger patient population and time scalethan was possible during the initial clinical

trials. Such adverse effects detected byphase-IV trials may result in thewithdrawal or restriction



W orld Health Organization

http://www.who.int for ³ the International

Clinical Trials Registry Platform´

National Institutes of Healthhttp://www.clinicaltrials.gov

http://www.nih.gov

National Cancer Institute

http://www.cancer.govCenters for Disease Control and Prevention

http://www.cdc.gov

Know more about RCT




� 7) Meta Analysis : Statistical analysis combining

results of several independent studies

considered combinable by the researcher.

� It is like a review of articles but in contrast to it, itattempts to analyze statistically aggregate

results to derive an integrated conclusion

� Faces problems due to ± publication bias and

varying quality of studies



I hope I haven¶t done this to you!



THANK YOU !

STUDY DESIGNS for Adilabad

Documents

Transcript of STUDY DESIGNS for Adilabad