Associate Professor Department of Community Medicine JSSMC Mysore Decision No1 Alter the events under study Observational study Experimental Study No Yes Decision No 2 Make measurements on more than ID: 911840
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Slide1
Study designs
Dr. Praveen KAssociate ProfessorDepartment of Community MedicineJSSMC, Mysore
Slide2Decision No.1
Alter the events under study
Observational study
Experimental Study
No
Yes
Slide3Decision No. 2
Make measurements on more thanone occasion
Cross-sectional study Longitudinal study No
Yes
Slide4Past
Future
Retrospective study
Prospective Study
Decision No. 3Deal exclusively with past or with future
Slide5What you want to do to generate the hypothesis to test the hypothesis
to Develop / accept a new Rx
Slide6Study designs
Observational
Experimental
RCT
Case control
Cohort
Descriptive
Analytical
Case report
Cross sectional
Longitudinal
Case series
Non Randomized
Slide7Descriptive studies
Slide8Case reportA rare presentation of renal carcinoma
A unusual presentation of thyroid swellingA rare case of emphysematous pyelonephriitis.An unusual presentation of tubercular hepatitis
Slide9Malformed limbs in Thalidomide tragedy
Slide10Case Reports/ Case Series
The most basic descriptive study.Link between clinical medicine and epidemiologyHypothesis generating.Rarely the evidence can even be strong!!
Slide11Descriptive study
Define the populationDefine the diseaseDescribe the diseaseTimePlacepersonMeasure the diseaseCompare with known indicesFormulate the hypothesis
Slide12Uses of descriptive studies
Magnitude of the health problemHelps in formulating the hypothesisProvides further areas for research
Slide13Descriptive studies can be Cross-sectional studyLongitudinal study
Slide14Cross Sectional studies
Evidence-based Chiropractic14
Health status
Exposure levels
At one point in time
Slide15Example for cross sectional study
Slide16Slide17Example for Longitudinal studies
Slide18Analytical study
Aim of Analytical Studies is to find outWhether or not any association exists between cause and effect.If exists what is the strength of the association.
Slide19ANALYTICAL STUDIESThere are two types of studies
a. Case control study b. Cohort study
Slide2020
Case-control study design
Slide21DISTINCTIVE FEATURES:-Both exposures and outcome (disease) have occurred before the start of the study.
The study proceeds backwards from effect to cause.It uses a control or comparison group to support or refute an inference.
Slide22Frame work
Suspected factors Cases (disease present)
Controls (disease absent)
Present
Absent
A
B
C
D
Example- cigarette smoking vs. lung cancer
Lung cancer= A+C
Suitable controls=B+D
If
frequency of
smoking A/A+C > B/B+D
An
association is said to exist between smoking and
Lung
cancer
Total
A+C
B+D
Slide23Basic stepsSelection of cases and controls
MatchingMeasurement of exposureAnalysis 1.estimation of risk 2.odds ratio
Slide24Example of case control study
Slide25Cohort study
A population is identified
One cohort is exposed to a risk factor, while the other is not
Slide26Important Features of Cohort Design
Follow upCalculation of incidence among exposed and non-exposedEstimation of riskRelative riskAttributable risk
Slide27Example of cohort study
Slide28Randomized Control Trial (RCT)
Slide29STEPS IN CONDUCTING RCT
STEP 1. THE PROTOCOL
Specify
: the aims and objectives of the study
Strict criteria should be followed for inclusion in the trialSample size should be sufficient to get valid resultsStandardization of working procedures Responsibility of the parties involved in the trial should be specified
Slide30Strict follow up of the protocol – reduces bias & reduces source of error in study
“Pilot study” – Feasibility of study - Operational efficiency - Acceptability
Slide31STEP 2: SELECTING REFERENCE POPULATION
Population to which the findings of the trial if found successful are expected to applicableSTEP 3: SELECTION OF STUDY POPULATION
derived from reference population
Criteria :
Written consent after explaining the purpose , procedure & dangers of the studyDerived from reference populationEligible for the trial STEP 4: RANDOMIZATIONProcedure by which participants are allocated into study and control groups
Slide32STEP 5: MANIPULATION
Study group- we intervene by deliberate application or withdrawal of the suspected risk factor
Control group –NO intervention (use placebo)
The intervention (drug ,vaccine, new procedure) is called independent variable
The final outcome constitutes dependent variable
Slide33STEP 7: ASSESSMENT
After tabulation of data assessment is done by means of statistical significance test .Positive results –decrease in incidence of disease or improvement of the patientsNegative results – side effects of drug, death
Slide34Slide35Slide36Thank You !
Working towards positive health