Dr Seyyed Alireza Moravveji MD Community Medicine specialist

Dr Seyyed Alireza Moravveji MD Community Medicine specialist

Epidemiologic Study Designs Descriptive studies Examine patterns of disease Analytical studies Studies of suspected causes of diseases Experimental studies Compare treatment modalities Dr Seyyed Alireza Moravveji MD Community Medicine specialist

Epidemiologic Study Designs Dr Seyyed Alireza Moravveji MD Community Medicine specialist

Research Study Design observational no DECISION: Alter the events under study? yes experimental Dr Seyyed Alireza Moravveji MD Community Medicine specialist Examples - case report - case series - cross-sectional - case-control - cohort - RCT - basic science

Hierarchy of Epidemiologic Study Design Dr Seyyed Alireza Moravveji MD Community Medicine specialist

Allocation of Exposure ﺗﺨﺼیﺺ ﺩﺍﺩﻥ ﻣﻮﺍﺟﻬﻪ ﺑﻪ گﺮﻭﻫﻬﺎی ﺗﺤﺖ ﻣﻄﺎﻟﻌﻪ Experimental Study Observational Study group Random Allocation Nonrandom Allocation Group A Group B Group A Dr Seyyed Alireza Moravveji MD Community Medicine specialist Group B

Design of Interventional studies Reference Population Experimental Population Non-Participants Treatment Allocation Treatment Group Cooperators Non-Cooperators Comparison Group Cooperators Dr Seyyed Alireza Moravveji MD Community Medicine specialist Non-Cooperators

Dr Seyyed Alireza Moravveji MD Community Medicine specialist

Dr Seyyed Alireza Moravveji MD Community Medicine specialist

ﻃﺮﺡ کﻠی کﺎﺭآﺰﻣﺎیی ﺑﺎﻟیﻨی EC Study Group SP SP = EC = R = T = Intervention T R No Intervention Study Population Eligibility Criteria Randomize intervention Elapsed time Dr Seyyed Alireza Moravveji MD Community Medicine specialist Outcome No Outcome

Randomization Dr Seyyed Alireza Moravveji MD Community Medicine specialist

? Who gets which treatment • To conduct a good experiment, “treatment assignments” must be “random. ” • “Random” means everybody has an equal chance of getting a treatment. • “Haphazard” does not mean random! Dr Seyyed Alireza Moravveji MD Community Medicine specialist

? Who is in control • Every experiment should have a “control group. ” • People in control group are treated exactly the same way as the other people in the experiment, except they do not get the “active treatment. ” • A “placebo group” is a special kind of control group. Dr Seyyed Alireza Moravveji MD Community Medicine specialist

Confounding • Confounding is an apparent association between disease and exposure caused by a third factor not taken into consideration Dr Seyyed Alireza Moravveji MD Community Medicine specialist

Confounding • Confounding is an apparent association between disease and exposure caused by a third factor not taken into consideration Dr Seyyed Alireza Moravveji MD Community Medicine specialist

Confounding Dr Seyyed Alireza Moravveji MD Community Medicine specialist

Blinding or Masking • Non-Blind – All patients know treatment • Single Blind – Patient does not know treatment • Double Blind – Neither patient nor health care provider know treatment • Triple Blind – Patient, physician and statistician/monitors do not know treatment • Double blind recommended when possible Dr Seyyed Alireza Moravveji MD Community Medicine specialist

Double-Blinded Single-Blinded Dr Seyyed Alireza Moravveji MD Community Medicine specialist

Liver of the Nature Rt hepatic duct Large gall stone Common hepatic duct Dr Seyyed Alireza Moravveji MD Community Medicine specialist Cystic duct CBD

Dr Seyyed Alireza Moravveji MD Community Medicine specialist

Standard 2 × 2 Crossover Design Period 1 Period 2 W A Group 1 S H O Drug U T P E R I O Placebo D Crossover W A S H O Group 2 Placebo U T P E R I O D Dr Seyyed Alireza Moravveji MD Community Medicine specialist Drug

Crossover Design • Subjects are randomized to a sequence of two or more treatments • Each subject serves as his own control 1 Group Sequence I A, B A B II B, A B A Period Washout Dr Seyyed Alireza Moravveji MD Community Medicine specialist Period 2

Interventional studies Reference Population Experimental Population Non-Participants Treatment Allocation Treatment Group Cooperators Non-Cooperators Comparison Group Cooperators Dr Seyyed Alireza Moravveji MD Community Medicine specialist Non-Cooperators

Dr Seyyed Alireza Moravveji MD Community Medicine specialist

Dr Seyyed Alireza Moravveji MD Community Medicine specialist