using ebm to answer clinical queries

Using EBM to Answer Clinical Queries

Robin FeatherstoneClinical Medicine [email protected]://www.slideshare.net/featherr

Agenda

• Background vs. Foreground questions• Clinical evidence • Study types • Searching exercises

– Using PICO to refine questions– Searching down the levels of evidence

• Questions

EBM REFRESHER

Two Broad Question Categories

• Background = basic information about a subject

What is strabismus? What is a screening test for strabismus?

• Foreground = specific to a clinical scenarioIs Botulinum Toxin (Botox) more effective than surgery to improve cosmetic appearance for a patient with advanced strabismus?

Sources for Background Questions

Resource ExampleTextbook Robbins basic pathologyHandbook Adolescent medicine: a handbook for

primary careManual The Washington manual of surgeryEncyclopaedia Encyclopedia of respiratory medicineDictionaries Dorland’s pocket medical dictionary

Refine Foreground Questions using PICO

P = Patient or ProblemI = Intervention or ExposureC = ComparisonO = Outcomes

Determine your Question Type1,2

1. Aetiology: What is the cause of the disease and its mode of operation?

2. Diagnosis: How accurate is this diagnostic test?3. Prognosis: What is the probable course of the disease?4. Therapy: Is one intervention more effective than

another?5. Prevention: How to reduce the risk of this disease?6. Cost-effectiveness: Is one intervention more cost-

effective than another?7. Quality of life: What will be the patient’s quality of life?

1 Heneghan, Carl, and Douglas Badenoch. Evidence-Based Medicine Toolkit. 2nd ed. Malden, Mass.: BMJ Books/Blackwell Pub., 2006.2 Glover, Jan, and Lei Wang. Find it Fast: The Clinical Question : www.med.yale.edu/library/education/guides/screencasts/finditfast/finditfast_2/

Studies to Answer Each Type1,2

Type of Question Type of Evidence

Aetiology •Randomized controlled trials•Case-control or cohort studies•Case series

Diagnosis •Diagnostic validation studies•Prospective studies / blind comparison to a gold standard

Prognosis •Inception cohort studies•Case control studies•Case series

Therapy •Randomized controlled trials•Systematic reviews / meta-analyses

Prevention •Randomizes controlled trials•Cohort studies, case control studies•Systematic reviews / meta-analyses

Cost-effectiveness •Economic analyses

Quality of life •Qualitative studies1 Heneghan, Carl, and Douglas Badenoch. Evidence-Based Medicine Toolkit. 2nd ed. Malden, Mass.: BMJ Books/Blackwell Pub., 2006.2 Glover, Jan, and Lei Wang. Find it Fast: The Clinical Question : www.med.yale.edu/library/education/guides/screencasts/finditfast/finditfast_2/

Level of Evidence Pyramid

Qualitative Studies

CASE STUDIES AND SEARCHING EXERCISES

Case study 1

Refine this case into a question and identify the best study type to answer that question.

Your patient travels regularly on business and suffers frequently from the effects of jet lag. They’ve tried tomato juice and exercise but neither seems to help. They ask if there is anything else they can do?

Create an answerable question

Patient, Problem, or Population

Jet lag

Intervention

Comparison

Outcome(s) Reduced symptoms

What are the most clinically effective preventative measures for reducing the symptoms of jet lag?

Identify your question typeType of Question Type of Evidence


Diagnosis •Diagnostic validation studies•Prospective studies / blind comparison to a gold standard






Select a resource

Qualitative Studies

Exercise

Select one of the following resources to answer the question: What are the most effective preventative measures for jet lag?

1. Cochrane Library2. ACP’s PIER3. PubMed4. Google Scholar

Conclusions

• Number of results

Source Hits

Cochrane Library 2

ACP’s PIER 43

PubMed 561 (56 if using MeSH with prevention subheading)

Google Scholar About 78,300

Discussion

• How does the quality of these results compare?

• Which resource would you use in a clinical setting? In a research setting?

Case Study 2

A patient with breast cancer asks how women typically feel after mastectomy. How will her life differ after surgery?

What step should we take first to answer this question?



Patients following mastectomy

Intervention

Comparison

Outcome(s) Quality of life

What is the quality of life of patients following mastectomy?

Identify your question typeType of Question Type of Evidence


Diagnosis •Diagnostic validation studies•Prospective studies blind comparison to a gold standard






Select a resource

Qualitative Studies

Exercise

Search the following resources to answer the question: What is the quality of life of patients following mastectomy?

1. PsycINFO2. CINAHL3. Google Scholar

Conclusions

• Number of results

Source Hits

PsycINFO 10

CINAHL 92

Google Scholar about 21,900

Discussion

• How do qualitative questions compare to other question types?

• How do you assess the quality of these results?

Case Study 3

A patient expresses concern before cataract surgery about the amount of pain they will experience. You consider administering intracameral anaesthetic (lidocaine) as a supplement to topical anaesthetic, but you’re not sure if the additional anaesthesia will reduce intraoperative pain perception compared with topical anaesthetic alone.



Intervention

Comparison

Outcome(s)



Patients undergoing cataract surgery

Intervention Topic anaesthesia alone

Comparison Topical anaesthesia with intracameral lidocaine

Outcome(s) Reduction of pain perception

In cataract surgery patients, does topical anaesthetic alone reduce pain perception when compared to topical anaesthetic supplemented by intracameral lidocaine?

What kind of question is this?

Type of Question Type of Evidence


Diagnosis •Diagnostic validation studies•Prospective studies blind comparison to a gold standard






Select a resource

Exercise

Search whatever resource you think would best answer the question:

In cataract surgery patients, does topical anaesthetic alone reduce pain perception when compared to topical anaesthetic supplemented by intracameral lidocaine?

Results

• What resources did you search? • Did you find the answer to your question?

Summary

• Background vs. Foreground questions• Using PICO to formulate an answerable

question • Identifying question types• Identifying studies that best answer your

question• Searching down the levels of evidence

QUESTIONS?

using ebm to answer clinical queries

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