Assessment of Harm based on our Best Available Evidences in the EBM Workshop

Slide1Assessment of  Harm based  on  our  best available  evidences Assessment  of  Harm based  on  our  best available  evidences The  EBM  workshop The  EBM  workshop A.A.Haghdoost,  MD;  PhD  of  Epidemiology A.A.Haghdoost,  MD;  PhD  of  Epidemiology Ahaghdoost@kmu.ac.ir Ahaghdoost@kmu.ac.ir

Slide2EBM workshop: Assessment of HarmDr. A.A.Haghdoost Why should we assess Harm  To  choose  the  best  treatment  strategy  To  choose  the  best  treatment  strategy  To  address  to  public  questions  and  mass media  To  address  to  public  questions  and  mass media “Do  oral  contraceptives  cause  breast  cancer?” “Do  oral  contraceptives  cause  breast  cancer?” “Do  calcium  antagonists  increase  the  risk  of  death or  cancer?” “Do  calcium  antagonists  increase  the  risk  of  death or  cancer?”

Slide3EBM workshop: Assessment of HarmDr. A.A.Haghdoost Main steps  Systematic  search  Systematic  search  Check  the  validity  of  findings  Check  the  validity  of  findings  Evaluate  the  importance  of  findings  Evaluate  the  importance  of  findings  Assess  if  the  results  are  applicable  to our  setting  Assess  if  the  results  are  applicable  to our  setting

Slide4EBM workshop: Assessment of HarmDr. A.A.Haghdoost Concerns Are  the  results  of  published harm/aetiology  study  valid? Are  the  results  of  published harm/aetiology  study  valid? People  listen  to  mass  media much  more  than  expert People  listen  to  mass  media much  more  than  expert

Slide5EBM workshop: Assessment of HarmDr. A.A.Haghdoost Main question? 1. 1. Were there clearly defined groups of patients, similar in all important ways other than exposure to the treatment or other cause  Clinical trials  Cohorts  Case-controls  Case reports phocomelia  in  children  born  to  women  who took  thalidomide phocomelia  in  children  born  to  women  who took  thalidomide Continued  in  next  page Continued  in  next  page

Slide6EBM workshop: Assessment of HarmDr. A.A.Haghdoost Main question? Weaknesses Strengths Assessment Starting Point Design feasibility, generalizability internal validity adverse event status exposure status RCT susceptible to threats to internal validity feasible when randomization of exposure not possible adverse event status exposure status Cohort susceptible to threats to internal validity overcomes temporal delays, may only require small sample size exposure status adverse event status Case- Control

Slide7EBM workshop: Assessment of HarmDr. A.A.Haghdoost 2. Were treatments/exposures and clinical outcomes measured in the same ways in both groups? (was the assessment of outcomes either objective or blinded to exposure?)  More attention to positive group  Hawthorn effect Continued  in  next  page Continued  in  next  page Main question?

Slide8EBM workshop: Assessment of HarmDr. A.A.Haghdoost 3. Was the follow-up of the study patients sufficiently long (for the outcome to occur and complete)?  Long enough to present the adverse effect  Long follow up usually increases the number of censured records Continued  in  next  page Continued  in  next  page Main question?

Slide9EBM workshop: Assessment of HarmDr. A.A.Haghdoost 4. Do the results of the harm study fulfill some of the diagnostic tests for causation? · Is it clear that the exposure preceded the onset of the outcome? · Is there a dose–response gradient? · Is there any positive evidence from a “dechallenge– rechallenge” study? · Is the association consistent from study to study? · Does the association make biological sense? Main question?

Slide10EBM workshop: Assessment of HarmDr. A.A.Haghdoost Are the valid results of the harm study important? What is the magnitude and precision of the association between the exposure and outcome?  OR, RR  NNH (Number Needed for Harm)  PAF (Population attributable Fraction)  Cost-benefits

Slide11EBM workshop: Assessment of HarmDr. A.A.Haghdoost Can be applied on our setting 1. 1. Is our patient so different from those included in the study that its results don’t apply? 2. 2.  What is our patient’s risk of the adverse event? What is our patient’s potential benefit from the therapy? 3. 3. What are our patient’s preferences, concerns and expectations from this treatment? 4. 4. What alternative treatments are available?