1. Evidence-Based Medicine Prognosis
Dr. Sompid Kintarak
Department of Stomatology
Faculty of Dentistry, Prince of Songkla University

2. Steps in Practicing EBM
Convert the need for information into an answerable question.
Track down the best evidence with which to answer that question.
Critically appraise the evidence for its validity, impact, and applicability.
Integrate the evidence with our clinical expertise and our patient’s characteristics and values.

3. Steps in Practicing EBM
Convert the need for information into an answerable question.
Track down the best evidence with which to answer that question.
Critically appraise the evidence for its validity, impact, and applicability.
Integrate the evidence with our clinical expertise and our patient’s characteristics and values.

4. The Answerable Question

5. Good questions are the backbone of practicing EBM
Good questions are the backbone of practicing EBM. It takes practice to ask the well-formulated question.

6. Well-Built Clinical ?’s
Directly relevant to the care of the patient and our knowledge deficit.
Contains the following elements:
the patient or problem being addressed
the intervention or exposure being considered
the comparison intervention or exposure, when relevant
the clinical outcomes of interest.

7. Well Formulated ?’s
Focus on evidence directly relevant to patient’s needs and our particular knowledge needs.
Suggest high-yield search strategies.
Suggest forms that useful answers might take.
Help us to model life-long learning techniques for our colleagues and students.
Are answerable and, thus, reinforce the satisfaction of finding evidence that makes us better, faster clinicians.

8. Prognosis Questions

9. Steps in Practicing EBM
Convert the need for information into an answerable question.
Track down the best evidence with which to answer that question.
Critically appraise the evidence for its validity, impact, and applicability.
Integrate the evidence with our clinical expertise and our patient’s characteristics and values.

10. Hierarchy of evidence Cross-sectional survey
Anecdotal case report
Cross-sectional survey
Case series without a control
Case-control observational study
Cohort study with a literature control
Analyses using computer databases
Cohort study with a historical control group
Unconfirmed randomized controlled clinical trial
Confirmed definitive randomized controlled clinical trials
Systematic review of randomized controlled clinical trials
Hierarchy of evidence

11. Resources META-SEARCH ENGINES PrimeAnswers TRIP+ SUMSearch
SYSTEMATIC REVIEWS/META-ANALYSES
Cochrane Library
PubMed Clinical Queries using Research Methodology Filters
EVIDENCE GUIDELINES/SUMMARIES
AHRQ Evidence Reports
Clinical Evidence
AHRQ Preventive Services
CLINICAL RESEARCH CRITIQUES
ACP Journal Club
Bandolier 1994-
BestBETs
CASE REPORTS/SERIES, PRACTICE GUIDELINES, ETC
National Guideline Clearinghouse
PubMed

12. Steps in Practicing EBM
Convert the need for information into an answerable question.
Track down the best evidence with which to answer that question.
Critically appraise the evidence for its validity, impact, and applicability.
Integrate the evidence with our clinical expertise and our patient’s characteristics and values.

13. Are The Results Valid?
Was this a well designed study in a relevant population?
The best design of study to answer a prognosis question is a prospective cohort study.
1. Concealment means that the treating clinicians cannot guess the order of entry into the trial. Randomization is typically advertised. Concealment is not advertised. If randomization is done at a central location then concealment is typically assured.

14. Are The Results Valid?
1. Was a defined, representative sample of patients assembled at a common (usually early) point in the course of their disease? กลุ่มตัวอย่างที่ศึกษา อยู่ในระยะเดียวกันของโรคหรือไม่ โดยทั่วไปมักจะเป็นระยะเริ่มต้นของโรค
2. Was patient follow-up sufficiently long and complete?
ผู้ป่วยได้รับการติดตามผลครบถ้วนและนานพอหรือไม่
3. Were objective outcome criteria applied in a “blinded” fashion?
มีการ “blind” ลักษณะพื้นฐานข้อมูลผู้ป่วยและปัจจัยต่าง ๆ ที่จะมีผลต่อการพยากรณ์โรคแก่ผู้ประเมินผลลัพธ์ที่ศึกษาด้วย เพื่อไม่ให้เกิดการลำเอียง
4. If subgroups with different prognosis are identified:
- Was there adjustment for important prognostic factors?
- Was there validation in an independent group of “test-set” patients?
1. Concealment means that the treating clinicians cannot guess the order of entry into the trial. Randomization is typically advertised. Concealment is not advertised. If randomization is done at a central location then concealment is typically assured.

15. Types of Studies Most studies will be “cohort studies”.
RCT’s (particularly placebo arms) can generate information about prognosis of disease.
Case-control studies can be useful but fail to provide estimates of absolute risk. Mostly encountered when the outcome is rare or required duration of follow-up is long.

16. The Cohort of Patients
How close to “ideal” does the study come in terms of how the disease was defined and how the participants were assembled (“full spectrum of illness”).
e.g. avoid “referral bias” if possible
Is this an “inception” cohort or is there uniform entry point (for late stage disease)?
start smoking
atherosclerosis
lung cancer
death
start smoking
atherosclerosis
smoking cessation program
lung cancer
death

17. Follow-up
To know if length of follow-up sufficient often requires general knowledge about disease.
Complete follow-up is critical. Failure is influenced both by better than average and worse than average clinical course.
“5% and 20%” rule
worst-case scenario/sensitivity analysis

18. Outcome Criteria
Extreme outcomes are easy to recognize. Outcomes in between require judgement and thus require standard criteria.
Those making judgement are kept “blind” to patients’ clinical characteristics and prognostic factors.

19. Adjustment and Validation
If subgroups with different prognosis then was there statistical adjustment for other important prognostic factors (statistical adjustment is not explanatory).
To the extent that adjustment is not explanatory, the first time a prognostic factor is identified, is there a confirmatory data set of patients (“derivation set” and “validation sets”).

20. Clinically Important? How likely are the outcomes over time?
Percentage “survival” at a particular point in time.
Median survival.
Survival curves.
How precise are the prognostic estimates?
95% CI - range of values within which we can be 95% sure that the population value lies

21. Survival Curves 1 year survival 95% Median survival unknown
Median survival 3 months
1 year survival 20%
Median survival 9 months
1 year survival 20%
Median survival 7 months

22. Applicable to Our Patient?
1. Are the study patients similar to our own?
2. Will the evidence make a clinically important impact on our conclusions about what to offer or tell our patient?

23. References
. บทที่ 3. การประเมินคุณภาพของข้อมูล ใน: การเรียนการสอนการแพทย์เชิงประจักษ์ – Learning and teaching of evidence-based medicine. พิมพ์ครั้งที่ 1. กลุ่ม Promoting evidence-based medicine into clinical practice คณะแพทยศาสตร์ มหาวิทยาลัยสงขลานครินทร์ หน้า
Sackett DL, Straus SE, Richardson WS, Rosenberg W, Haynes RB. Evidence-based medicine – how to practice and teach EBM. Second ed. Edinburgh: Churchill Livingstone, pp
Clarkson J, Harrison JE, Ismail AI, Needleman I, Worhtington H. Evidence based dentistry for effective practice. London: Martin Dunitz, 2003.