Optimal Ways to learn about and communicate Evidence Based Medicine Misbah Keen, MD, MBI, MPH Matthew J. Thompson, MD, MPH, DPhil

The Problem EBM courses and programs exist at all levels of Medical Education Very few (if any) courses / programs result in behaviour change or practice improvement

Audience Exercise -1 Alice, a 45 year old woman with a positive screening mammogram asks your opinion about her chances of this actually being breast cancer. Mammography is 90% sensitive and 90% specific and the prevalence of breast cancer in her age group is 1%. 

Answer Multiple studies have looked at a similar question. 3 Countries Over 1000 physicians ranging from Residents to Department Chairs

Answer 95 % got the answer wrong (2% +/-) Vast majority of the wrong answers were 10 times more than the actual probability.

Use Natural Frequencies

After doing some reading, you find that for men of his age: Example Your father went to his doctor and was told that his test for a disease was positive. He is really worried, and comes to ask you for help! After doing some reading, you find that for men of his age: The prevalence of the disease is 30% The test has a sensitivity of 50% and specificity of 90% “Son, tell me what’s the chance I have this disease?”

Prevalence of 30% Sensitivity of 50% Specificity of 90% 22 people test positive………. of whom 15 have the disease About 70% Disease +ve 15 30 100 Testing +ve 7 70 Disease -ve

Try it again A disease with a prevalence of 4% must be diagnosed. It has a sensitivity of 50% and a specificity of 90%. If the patient tests positive, what is the chance they have the disease?

Prevalence of 4% Sensitivity of 50% Specificity of 90% 11.6 people test positive… of whom 2 have the disease About 17% Disease +ve 2 4 100 Testing +ve 96 9.6 Disease -ve

Audience Exercise -2 Alice, a 45 year old woman with a positive screening mammogram asks your opinion about her chances of this actually being breast cancer. Mammography is 90% sensitive and 90% specific and the prevalence of breast cancer in her age group is 1%. 

Prevalence of 1% Sensitivity of 90% Specificity of 90% 108 people test positive… of whom 9 have the disease About 8.3 % Disease +ve 9 10 1000 Testing +ve 990 99 Disease -ve

Prevalence of 1% Sensitivity of 95% Specificity of 95% 59 people test positive… of whom 9.5 have the disease About 16 % Disease +ve 9.5 10 1000 Testing +ve 990 49.5 Disease -ve

Prognosis Odds Ratio

Therapeutics Relative Risk vs Absolute Risk Number Needed to Treat

Communicating Evidence

Audience Exercise - 1 Communicating Evidence

Communicating Evidence - Problems Physicians ask if patients have questions about treatments less than half the time Patient’s understanding of risks and benefits is “rare” Patients may not always “hear” what is being presented to them.

Communicating Evidence - Best Practices Use plain language to make written and verbal materials more understandable. Present data using absolute risks. Present information in pictographs if you are going to include graphs. Present data using frequencies.

Picture display of the benefits of 10 years of aspirin chemoprevention among 1,000 persons with a 10 percent 10-year global risk of coronary heart disease (CHD). Green faces represent the number of patients who would not benefit because they are not among the 10 percent predicted to have a CHD-related event. The red faces represent the number of patients who would have an event despite taking aspirin. The yellow faces represent patients who would not have an event because they took aspirin (i.e., the number of patients who would benefit).

Communicating Evidence - Best Practices Use an incremental risk format to highlight how treatment changes risks from preexisting baseline levels. Be aware that the order in which risks and benefits are presented can affect risk perceptions. Consider using summary tables that include all of the risks and benefits for each treatment option.

Communicating Evidence - Best Practices Recognize that comparative risk information (eg, what the average person’s risk is) is persuasive and not just informative. Consider presenting only the information that is most critical to the patients’ decision making, even at the expense of completeness. Repeatedly draw patients’ attention to the time interval over which a risk occurs.

Shared Decision Tools http://shareddecisions.mayoclinic.org/ https://decisionaid.ohri.ca/index.html

Audience Exercise - 2 Communicating Evidence