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Types of studies

Types of studies

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Types of studies

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  1. Types of studies Behnam Shakiba Students Scientific Research Center (SSRC) Tehran University of Medical Sciences B.Shakiba

  2. Types of studies • primary Observational Experimental (interventional) • Secondary (review article) Narrative systematic B.Shakiba

  3. Experimental studies An “experiment” deliberately imposes some “treatments” on individuals to see if the treatments have an effect on some “outcome” or measurement. B.Shakiba

  4. Example of an experiment Population #1 Population #2 Ascorbic Acid Placebo Outcomes: Do the average number of colds differ? Do their average lengths of colds differ? B.Shakiba

  5. Observational studies • Descriptive study • Analytical study B.Shakiba

  6. Descriptive studies Five “W” questions: Who What Why When Where So What B.Shakiba

  7. Types of descriptive studies Case report Describe the experience of asingle patient B.Shakiba

  8. Types of descriptive studies Case report Late-onset multiple sclerosis mimicking brain tumor: a case report. A case report: Kikuchi-Fujimoto disease B.Shakiba

  9. Types of descriptive studies Case-series report Collection of more than 1 case which occure in a short period. B.Shakiba

  10. Type of descriptive studies Case-series report Eosinophilic meningitis: a case series report Histoplasmosis in pregnancy: a case series report B.Shakiba

  11. Types of descriptive studies Surveillance • The key feature here is feedback • Prevention and control of the problem B.Shakiba

  12. Types of descriptive studies Surveillance Plesiomonas shigelloides-associated diarrhoea in Bangladeshi children: a surveillance study. Antimicrobial susceptibility of community-acquired respiratory tract pathogens in North America. B.Shakiba

  13. Type of descriptive studies Cross-sectional studies: • survey or a prevalence study • examine the presence or absence of disease and the presence or absence of an exposure at a particular time B.Shakiba

  14. Types of descriptive studies Cross-sectional studies: Nutritional knowledge, food habits and health attitude of Chinese university students Prevalence of obesity and glucose homeostasis in psychiatric patients taking antipsychotic drugs B.Shakiba

  15. Types of descriptive studies • Case report • Case series • Cross sectional • Surveillance B.Shakiba

  16. Use of descriptive studies • Trend analysis • Planning • clues about causes B.Shakiba

  17. Danger A temporal association is incorrectly inferred to be a causal one. B.Shakiba

  18. B.Shakiba

  19. Analytical studies • Cohort studies • Case Control studies • Cross sectional studies B.Shakiba

  20. Cohort studiesA cohort study follows-up two or more groups from exposure to outcome. B.Shakiba

  21. Cohort studies B.Shakiba

  22. Cohort studies • Depression and anxiety in women with early breast cancer • Risk of cancer after the diagnosis of Parkinson's disease B.Shakiba

  23. Cohort studies Advantages: • ascertain incidence and natural history • sequence between cause and outcome is clear • investigation of multiple outcomes • assessment of many outcomes • study of rare exposures B.Shakiba

  24. Cohort studies Disadvantages: • Selection bias • rare diseases • Loss to follow up • Large sample size • Latency period • Cost • Time consuming B.Shakiba

  25. Case control studies • epidemiologists use them to study a huge variety of associations. • more frequently than other analytical studies B.Shakiba

  26. Case-control study Exposure Disease (+) ? -------------------------------------------- Exposure Disease (-) ? -------------------------------------------- Investigator B.Shakiba

  27. Case control study B.Shakiba

  28. Case control studies • Smoking and non-Hodgkin lymphoma • Plasma prolactin in patients with colorectal cancer. B.Shakiba

  29. Case control studies Advantages: • Rare diseases • Several exposures • Long latency • Rapidity • Low cost • Small sample size • No ethical problem B.Shakiba

  30. Case control studies Disadvantages: • Selection bias • Measurement of exposure information • Control of confounding factors • Not suitable for rare exposure B.Shakiba

  31. Type of studies B.Shakiba

  32. B.Shakiba

  33. Types of Studies Retrospective (or case control) Study Data are collected from the past Prospective (or Longitudinal or Cohort) Study Data are collected in the future B.Shakiba

  34. Secondary studies (review) • Narrative • systematic B.Shakiba

  35. Examples??? • Depression and anxiety in sclerodermia • Mortality and cancer incidence in a Swedish art glassworks • Prevalence of asthma and allergy in schoolchildren in Belmont, Australia B.Shakiba

  36. H N T N N A S A K H T K H S N K H T H K H S K N S A K K T N N H N T A N S N H H S A T H K K H K T K T N N S N K S N T N A S N T H T N K K S H N B.Shakiba