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Flashcards

Case control Studies

maxytrejo1 Epid college English 42 cards

Cards in this deck (42)

  1. 1Dsighn of the Case control Studiesstart with population then go back to the cases ( with dis) and control ( w/o dis) then each have exposed and unexposed. Time moves forward, and the direction of inquary moves back
  2. 2In case selction, there is an established specific criteria for __diagnosis and inclusion of cases
  3. 3One method for case selection involoves__ascertaining cases from a well defined source population such as : hospitals, HMOs, disease registries, advertisements
  4. 4An alternative in Case selection includesselecting a probability sample of cases from the population
  5. 5In swlcting incident and prevalent cases, the objective is toensure that exposure preceded the outcome ( temporal sequence)
  6. 6Temporal sequencing iswhen the exposure precedes the outcome
  7. 7In Case control studies we prefer to use___BUTincidient cases BUT the determination of incident cases is not so easy
  8. 8Incident cases are usually defined as____ BUTnewly diagnosed cases BUT the date of diagnosis is used as a proxy for disease initiation
  9. 9Control selection os often the most difficult becyaseof the potential for bias
  10. 10Many beleive that control should berepresentative of a source population, that is the population from which cases and control origintate
  11. 11Source populationpopulation form which cases and controls originate
  12. 12What are some comman used controlsPopulation based, hospital based, neighbors of cases and less frequently used are friends, school mates and siblings
  13. 13Controls: Hospital - based controls arePersons seeking medical care at the "same institutions" as the cases for conditions believed "unrelated" tot he cases' diagnosis
  14. 14Hospital Control are used becuase1. Convenience 2. Already have diagnosis(don't need confirmation) 3. Easy to collect blood and other specimens 4. Compliance from a 'captive audience'
  15. 15Major concerns with hospital controls are thatstudy base principle may be violated: an urban teaching hospital may provide primary care to the poor and tertiary care to wealthy/insured
  16. 16A concern with hospital control:Exposure distribution "may" fundamentally differ between study bases of cases and controls
  17. 172 majore concers with hispital controls1. study base principle may be violated 2. exposure may fundamentally differ between study bases of cases and controls
  18. 18When comparing hospital cases to population based controls, will the study base of controls and cases differ? Will hosp cases differ in exposure odds vs. controls as a function of the study base?THis is likely when examining risk factors such as smoking: smoking is more prevalent among hospitalized patieints
  19. 19Should we exclude hospital bases control admitted for exposure related diseases? ex: in a case control study of smoking and lung cancerHospital cases: lung caner patiens, Hospital control: empysema patients, Result: underestimate the effect of smoking on lung cancer
  20. 20What is there is a negative association between the exposure and disease diagnosis of the control group?The control groups may have a "lower than expected exposure prevalence" compared to the cases
  21. 21What are the 2 alternatives for examing controls speratley as subgroups1. Examine different controls separately as subgroups 2. Select patients with a variety of diagnosis as a single control group
  22. 22Selecting patients with a variety of diagnosis as a single control group does what?minimizes the impact of bias if any one disease is highly associated (positive/neg) with the exposure
  23. 23Example: study of coffee consumption and pancraitec cancerHosp Cases: pancreatic cancer patients Hsop Controls: patients( w peptic ulcer) identified form gastro. Reslut: Overestimate the effect of coffee cosumption
  24. 24In exposure assesment, what are some sources of exposure informationpersonal interview or self administered questionarre, medical records, biospesies, other.
  25. 25In assessing exposure, it is important thatexposure data in controls should be of same quality and availability as in cases
  26. 26What is one of the limitations of recalling exposure1. people may not remember accurately info being requested2. If extent of recall differs systematical between cases and control "recall bias"
  27. 27People not rembering acuratley informing being requested what happens?If the limitation is equal in cases and controls, (non differnential misclassification) then there is bias towards the null hypothesis
  28. 28What is non differntial misclassificationlimitation i equal in cases and controls
  29. 29If extent of recal differs systematically between cases and controls then there is arecall bias
  30. 30What is an example of a confounding in case control studyrisk factor is coffee drinking , causes pancreatic cancer BUT Confounder: cigarette smoking
  31. 31What are 2 solutions for counfounding in case control studies1. Can match cases and controls on the confounder of interest not the Risk factor, 2. The confounder can be controlled for in the analysis phase
  32. 32What are 2 advantages of case control studies1. Assures comparability of cases and controls on the selected variables. 2.Can control for "unmeasured confounders" that are difficult to quantify: match on neighborhood as a proxy of socioeconomic
  33. 33What are 3 disadvantages of case control studies?1. Difficult/costly to find sufficient number of controls that meet criteria 2. Effects of matched variable on outcome cant be assessed 3. Potential for overmatching
  34. 34In case control studyexposure history is recalled over some period in the past
  35. 35What are 5 limitations of case control study1. limited information available ( retrospective available) 2. only one outcome can be studied 3. cant estimate incidence of disease 4. Cant assess development changes 5. Most daunting challenge: Baisis
  36. 36Limitations of case control" Most daunting challenge: Biases explainBasis in selecting cases and in particular control, recall biasis
  37. 37A hybrid desighn is also known asnested case control study
  38. 38In a hybrid desighn isa study design incorporating both a prospective cohort study and case control study
  39. 39In a hybrid desighn:a study population gets divided into those who 1. develop disease and 2. those who do not develop disease, then into cases and control
  40. 40Whats are some advantages of a nested case control studyRecall bias is likley eliminated since exposure data is obtained prior to disease develpment
  41. 41Whats are some advantages of a nested case control study (2)Costs are reduces comapred to prospective cohort studies (lab tests are only preformed among cases and controls)
  42. 42Whats are some advantages of a nested case control study (3).Controls are selected from the same population from which the cases had arisen

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college Epid (Final) Flashcards on Case control Studies, created by maxytrejo1 on 13/05/2014.
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