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Introduction to Critical Appraisal

Introduction to Critical Appraisal. Yulia Lin, MD, FRCPC Transfusion Medicine & Hematology Sunnybrook Health Sciences Centre University of Toronto TMR Journal Club, September 21, 2010. Why is Critical Appraisal important?. Vast amount of literature. New Studies in Transfusion.

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Introduction to Critical Appraisal

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  1. Introduction to Critical Appraisal Yulia Lin, MD, FRCPC Transfusion Medicine & Hematology Sunnybrook Health Sciences Centre University of Toronto TMR Journal Club, September 21, 2010

  2. Why is Critical Appraisal important?

  3. Vast amount of literature

  4. New Studies in Transfusion

  5. New Studies in Transfusion Past Studies in Transfusion

  6. New Studies in Transfusion Studies in other Sub-specialties Past Studies in Transfusion

  7. Why critical appraisal is important? • Impossible to keep up with all of the literature • Enables us to distinguish stronger evidence from weaker evidence • Allows us to appropriately incorporate the evidence into our practice so as to improve patient care

  8. Scholar • 2 - Evaluate medical information and its sources critically, and apply this appropriately to practice decisions • Describe the principles of critical appraisal • Critically appraise retrieved evidence in order to address a clinical question • Integrate critical appraisal conclusions into clinical care • Critically review published literature and apply appropriate utilization principles/practices /guidelines

  9. Purpose of TMR Journal Club • To present a recent article in the transfusion literature • To learn how to critically appraise the medical literature

  10. Steps to a successful JC • Choosing the article • Presenting the article • Critically appraising the article

  11. Choosing an article… • Where to find an article? • Recent table of contents • NEJM, Lancet, JAMA • Transfusion, Vox Sanguinis, Blood, etc. • Transfusion Medicine Reviews – Journal Club • Transfusion Medicine Community • List of interesting articles

  12. Choosing the article… • Which article? • Relevant • Interesting to you • What type of article? • Any article • But some are easier than others…

  13. Type of articles • Randomized controlled trials – Therapy • Observational studies – Harm • Systematic Reviews • Guidelines • Diagnosis • Prognosis

  14. First, a review…

  15. Randomized Controlled Trial Intervention A Population Outcomes measured Randomization Intervention B

  16. Randomized Controlled Trial Intervention A Population Outcomes measured Randomization Intervention B • Effects of tranexamic acid on death, vascular occlusive • events, and blood transfusion in trauma patients with • significant haemorrhage (CRASH-2): a randomised, • placebo-controlled trial. CRASH-2 trial collaborators. • Lancet. Published online June 15, 2010.

  17. Randomized Controlled Trial Placebo Trauma pts with Hemorrhage Death in hospital within 4 wks Randomization Tranexamic acid • Effects of tranexamic acid on death, vascular occlusive • events, and blood transfusion in trauma patients with • significant haemorrhage (CRASH-2): a randomised, • placebo-controlled trial. CRASH-2 trial collaborators. • Lancet. Published online June 15, 2010.

  18. Observational Case-Control Population Exposure to Risk Factor Exposed Cases (+Disease) Yes No Control (No disease) Yes No

  19. Observational Case-Control Population Exposure to Risk Factor Exposed Cases (+Disease) Yes No Control (No disease) Yes No Retrospective

  20. Observational Case-Control Population Exposure to Risk Factor Exposed Cases (+Disease) Yes No Control (No disease) Yes No Prevalence of xenotropic murine leukaemia virus-related virus in patients with chronic fatigue syndrome in the Netherlands: retrospective analysis of samples from an established cohort. Van Kuppeveld et al. BMJ 2010;340:c1018.

  21. Observational Case-Control Population Exposure to XMRV Exposed CFS (+Disease) Yes No Controls (No disease) Yes No Prevalence of xenotropic murine leukaemia virus-related virus in patients with chronic fatigue syndrome in the Netherlands: retrospective analysis of samples from an established cohort. Van Kuppeveld et al. BMJ 2010;340:c1018.

  22. Observational Cohort Cohort without Disease Population Exposure to Risk Factor Disease Yes No Exposed Cohort Yes No Not exposed

  23. Cohort Studies Past Present Future Cohort assembled Follow-up Retrospective Cohort Study

  24. Cohort Studies Past Present Future Cohort assembled Follow-up Retrospective Cohort Study Effect of duration of red blood cell storage on early and late mortality after CABG. van Straten et al. J Thor CV Surg 2010; published online.

  25. Cohort Studies Past Present Future Mortality before 30 days Mortality after 30 days CABG 1998-2007 Exposure to blood of different storage age Effect of duration of red blood cell storage on early and late mortality after CABG. van Straten et al. J Thor CV Surg 2010; published online.

  26. Cohort Studies Past Present Future Trauma 2000-2005 Nonmassive transfusion In-hospital mortality Plasma transfusion Effect of duration of red blood cell storage on early and late mortality after CABG. van Straten et al. J Thor CV Surg 2010; published online. Impact of plasma transfusion in trauma patients who do not require massive transfusion. Inaba et al. J Am Coll Surg June 2010;210:957-65.

  27. Cohort Studies Past Present Future Cohort assembled Follow-up Retrospective Cohort Study Cohort assembled Follow-up Prospective Cohort Study

  28. Cohort Studies Past Present Future Cohort assembled Follow-up Retrospective Cohort Study Cohort assembled Follow-up Prospective Cohort Study Transfusion practice and guidelines in Australian and New Zealand intensive care units Intensive Care Med 2010;36:1138-46.

  29. Cohort Studies Past Present Future Cohort assembled Follow-up Retrospective Cohort Study Patients receiving transfusion Adherence to guidelines Transfusion Indications & triggers Transfusion practice and guidelines in Australian and New Zealand intensive care units Intensive Care Med 2010;36:1138-46.

  30. Systematic Review • Overview • Summary of the medical literature that attempts to address a focused clinical question • Systematic review • Using methods designed to reduce the likelihood of bias • Meta-analysis • Review that uses quantitative methods to summarize the results

  31. Systematic Review • Systematic review • Using methods designed to reduce the likelihood of bias • Meta-analysis • Review that uses quantitative methods to summarize the results Intravenous immunoglobulin for Guillain-Barre Syndrome. Hughes et al. Cochrane Database Syst Rev 2010 Jun 16;6:CD002063.

  32. Guidelines • “Systematically developed statements to assist practitioner and patient decisions about appropriate health care for specific clinical circumstances” • Attempt to address all issues and values relevant to a clinical decision • Attempt to distill a large body of medical expertise into a convenient, readily usable format • Make explicit recommendations with definite intent to influence what clinicians do Field MJ. Clinical practice guidelines. 1990 Hayward et al. JAMA 1995;274:570-4 Cook et al. Ann Int Med 1997;127:210-6

  33. Guidelines • “Systematically developed statements to assist practitioner and patient decisions about appropriate health care for specific clinical circumstances” Perioperative blood transfusion and blood conservation in cardiac surgery: the Society of Thoracic Surgeons and The Society of Cardiovascular Anesthesiologists clinical practice guideline. Ann Thorac Surg 2007 May;83(5Suppl):S27-86. Guidelines on the use of irradiated blood components. BCSH 2010. http://www.bcshguidelines.com/pdf/draft_irrad_0710.pdf

  34. How to do a critical appraisal?

  35. Critical appraisal methods • Most are based on Users’ Guides to the Medical Literature • Available in a textbook form (2nd ed) • Brief version http://www.ebem.org/usersguide.html • For guidelines, different instruments • AGREE instrument: http://www.agreetrust.org/resource-centre/agree-ii/

  36. Steps to Critical Appraisal • Are the results valid? • Have the results been influenced in a systematic fashion so as to lead to a false conclusion? • What are the results? • How can I apply the results to patient care?

  37. RCT Intervention A Population Outcomes measured Randomization Intervention B

  38. RCT - Are the results valid? Intervention A Population Outcomes measured Randomization Intervention B Was the assignment of patients to treatment randomized?Were all patients who entered the trial accounted for and attributed at its conclusion?Were patients, clinicians and study personnel kept "blind" to treatment received?Were the groups similar at the start of the trial?Aside from the experimental intervention were the groups treated equally?

  39. RCT - What were the results? Intervention A Population Outcomes measured Randomization Intervention B How large was the treatment effect? How precise was the estimate of the treatment effect?

  40. RCT - How can I apply the results to patient care? Intervention A Population Outcomes measured Randomization Intervention B Can the results be applied to my patients?

  41. RCT - How can I apply the results to patient care? Intervention A Population Outcomes measured Randomization Intervention B Can the results be applied to my patients?Were all clinically important outcomes considered? Are the likely treatment benefits worth the potential harm and costs?

  42. Observational Cohort Cohort without Disease Population Exposure to Risk Factor Disease Yes No Exposed Cohort Yes No Not exposed

  43. Cohort - Are the results valid? Cohort without Disease Population Exposure to Risk Factor Disease Yes No Exposed Cohort Yes No Not exposed Except for the exposure under study, were the compared groups similar to each other?Were the outcomes and exposures measured in the same ways in both groups?Was the follow-up of patients sufficiently long and complete?Is the temporal relationship correct?Is there a dose-response gradient?

  44. Cohort - What are the results? Cohort without Disease Population Exposure to Risk Factor Disease Yes No Exposed Cohort Yes No Not exposed How strong is the association between exposure and outcome? Consider magnitude and dose response? How precise is the estimate of the risk?

  45. Cohort - How can I apply the results? Cohort without Disease Population Exposure to Risk Factor Disease Yes No Exposed Cohort Yes No Not exposed Are the results applicable to my patients?

  46. Cohort - How can I apply the results? Cohort without Disease Population Exposure to Risk Factor Disease Yes No Exposed Cohort Yes No Not exposed Are the results applicable to my patients?What is the magnitude of the risk?Should I attempt to stop the exposure?

  47. Putting it all together…

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