Welcome! Introductions. What is your name and role as an educator? What interested you in this session?

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2 Welcome! Introductions What is your name and role as an educator? What interested you in this session?

3 Biological Sciences Curriculum Study Established in 1958 Nonprofit organization Three areas of emphasis: Curriculum Development Professional Development Research and Evaluation

4 The 5As of Evidence-Based Medicine ASK ACQUIRE APPRAISE APPLY ASSESS

5 Funded by the National Institutes of Health Developed in collaboration with the Foundation for Blood Research in Scarborough, ME Targets advanced high school biology classes Two units: 1. Using Evidence-Based Medicine to Answer a Question of Therapy 2. Using Evidence-Based Medicine to Answer a Question of Diagnosis Field tested with more than 1800 students Use video case studies filmed in a major teaching hospital with an actual medical team

6 Science and Engineering Practices 1. Asking questions (for science) and defining problems (for engineering) 2. Developing and using models 3. Planning and carrying out investigations 4. Analyzing and interpreting data 5. Using mathematics and computational thinking 6. Constructing explanations (for science) and designing solutions (for engineering) 7. Engaging in argument from evidence 8. Obtaining, evaluating, and communicating information

7 So, what does the evidence-based medicine process look like in action? ASK Our case involves two young people who were tested for Lyme disease.

8 To test or not to test that is the diagnostic question. The scenario: While visiting a local shopping mall (Portland, ME) Alex and Emily come upon a kiosk offering a free screening test for Lyme disease. Both test positive and visit the doctor. The doctor asks about symptoms and hearing of none concludes that the odds of Alex having Lyme disease are 615 to 1 against but with Emily he is more concerned. How can this be?

9 ASK Patient s reason for being tested Alex Has been hiking in areas where there are ticks and plans to do more hiking in Colorado Emily Has recently been bitten by a tick Screening test result (ELISA) Positive Positive Other relevant evidence Dr. Erickson s recommendation No symptoms of Lyme disease No further action needed Probability of having Lyme disease is ~600 to 1 against No symptoms of Lyme disease Found an engorged tick on her neck Physical examination Diagnostic test (Western blot)

10 An evidence based medicine question (PICO) has four components: ASK P refers to the type of patients or populations refers to the test result or type of I intervention C refers to the comparison group or control test result O refers to the outcome (diagnosis) of interest

11 ASK Example of a PICO question: (P) In a teenager with autism, does (I) Galantamine compared to (C) placebo decrease the symptoms (O) of autism?

12 ASK How about (P) In a 22 year-old female with possible Lyme disease who has removed an engorged deer tick, does (I) a positive Lyme ELISA compared to (C) a negative ELISA increase the likelihood of a diagnosis (O) of Lyme disease?

13 What are the possible results from a screening test? Erythema migrans (rash, gold std) ACQUIRE Condition present Condition absent Screening test Positive a True Positive (+/+) b False Positive (+/-) Screening test Negative c False Negative (-/+) d True Negative (-/-)

14 Number with positive ELISA ACQUIRE Testing the Screening Test Lyme disease, n = 98 No Lyme disease, n = 139

15 ACQUIRE Results of the Study Erythema migrans (rash, gold std) Condition present Condition absent Screening test Positive a True Positive (+/+) b False Positive (+/-) Screening test Negative c False Negative (-/+) d True Negative (-/-)

16 ACQUIRE Results of the Study Erythema migrans (Gold Standard) Condition present Condition absent Screening test Positive a True Positive (+/+) 89 b False Positive (+/-) 39 Screening test Negative c False Negative (-/+) 9 d True Negative (-/-) 100

17 Analyzing the Screening Test APPRAISE Test Characteristic Sensitivity: The number of true positives (determined by the screening test) relative to the number of people with the condition (gold standard) Specificity: The number of true negatives (determined by the screening test) relative to the number of people without the condition (gold standard) False Positive Rate: The number of false positives (determined by the screening test) relative to the number of people without the condition (gold standard) False Negative Rate: The number of false negatives (determined by the screening test) relative to the number of people with the condition (gold standard) Calculation

18 Analyzing the Screening Test APPRAISE Test Characteristic Sensitivity: The number of true positives (determined by the screening test) relative to the number of people with the condition (gold standard) Specificity: The number of true negatives (determined by the screening test) relative to the number of people without the condition (gold standard) False Positive Rate: The number of false positives (determined by the screening test) relative to the number of people without the condition (gold standard) False Negative Rate: The number of false negatives (determined by the screening test) relative to the number of people with the condition (gold standard) Calculation a / (a + c) 89 / = 0.91 d / (b + d) 100 / = 0.72 b / (b + d) 39 / = 0.28 c / (a + c) 9 / = 0.09

19 APPRAISE Doctors use one more test parameter called the Likelihood Ratio (LR). The LR describes how confident you are that a patient has the condition after receiving a positive test result. Is the Likelihood Ration for the ELISA test clinically important?

20 How do doctors decide whether to give the test? Nomogram OAPR: Odds of being Affected given a Positive test Result

21 APPRAISE ACQIRE Nomogram To use the nomogram: 1. Locate the pre-test probability you will use. 2. Use a straight edge to form a line between the pre-test probability and the LR for Lyme ELISA (3.25) 3. Read off from the right hand axis the post-test probability

22 APPRAISE CQUIRE Using the Nomogram Pre-test Probability (as a percent) Post-test Probability (as a percent) Lyme Test LR = 3 Post-test Probability (as a percent) LR = 10

23 APPRAISE AQUIRE Using the Nomogram Pre-test Probability (as a percent) Post-test Probability (as a percent) Lyme Test LR = 3 Post-test Probability (as a percent) LR =

24 Patient s reason for being tested Alex Has been hiking in areas where there are ticks and plans to do more hiking in Colorado Emily Has recently been bitten by a tick ASK APPLY Screening test result (ELISA) Positive Positive Other relevant evidence Dr. Erickson s recommendation No symptoms of Lyme disease No further action needed Probability of having Lyme disease is ~600 to 1 against No symptoms of Lyme disease Found an engorged tick on her neck Physical examination Diagnostic test (Western blot)

25 APPRAISE ACQUIE But what about Dr. Erickson s claim that the odds of Alex having Lyme disease are 615 to 1 against? To answer that question we have one final calculation to perform We need to calculate the OAPR or the Odds of being Affected given a Positive test Result

26 APPRAISE Number of people to be tested 200,000 Based on Alex and Emily s location, Portland, ME with a population of 200K Number of people expected to have Lyme disease 100 Number of people expected not to have Lyme disease 199,900 Number of people with Lyme disease Test sensitivity Number of people without Lyme disease FPR of Test OAPR

27 APPRAISE Number of people to be tested 200,000 Number of people expected to have Lyme disease 100 Number of people expected not to have Lyme disease 199,900 Number of people with Lyme disease Test sensitivity = 91 Number of people without Lyme disease FPR of Test 199, = 55,972 OAPR = 91: 55,972 or 1 : 615

28 What do you think of Dr. Ericson s recommendation that Alex not be tested for Lyme disease? (Justify your repsonse) APPLY

29 How would you communicate the decision made by Dr. Ericson to Alex? To Emily? ASSESS

30 NGSS Practices of Science Which practices did you use during this session? What were you doing (or what would students do) to work on each practice?

31 NGSS Science Practice Asking questions Developing and using models Planning and carrying out investigations Analyzing and interpreting data Phase(s) of the EMB Process ASK ACQUIRE, APPRAISE Not used APPRAISE Using mathematics and computational thinking Constructing explanations Engaging in argument from evidence Obtaining, evaluating, and communicating information APPRAISE APPRAISE APPAISE, APPLY, and ASSESS ACQUIRE, APPLY, and ASSESS

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