Level of Evidence

Author: Derek Moore

Topic updated on 05/14/13 8:44pm

Introduction

A method utilized in evidenced based medicine to determine the clinical value of a study
See details of Clinical Design Trials

Different Levels of Evidence

Level 1	Randomized controlled trial (RCT) a study in which patients are randomly assigned to the treatment or control group and are followed prospectively Meta-analysis of randomized trials with homogeneous results
Level 2	Prospective cohort study a study in which patient groups are separated non-randomly by exposure or treatment, with exposure occurring after the initiation of the study
Level 3	Retrospective cohort study a study in which patient groups are separated non-randomly by exposure or treatment, with exposure occurring before the initiation of the study Case-control study a study in which patient groups are separated by the current presence or absence of disease and examined for the prior exposure of interest
Level 4	Case series a report of multiple patients with the same treatment, but no control group or comparison group
Level 5	Case report (a report of a single case) Expert opinion Personal observation

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(OBQ11.239) In the study by Moseley et al published in the New England Journal of Medicine, 180 patients with knee osteoarthritis were randomly assigned via sealed envelope to receive arthroscopic débridement, arthroscopic lavage, or placebo surgery. Outcomes were assessed by blinded evaluators at several points over a 2 year period with the use of five self-reported pain and function scores. There was a greater than 90% follow-up in the study. This study is best described as having which level of evidence? Topic

Review Topic

1. Therapeutic study, evidence level I
2. Therapeutic study, evidence level II
3. Diagnostic study, evidence level I
4. Diagnostic study, evidence level II
5. Prognostic study, evidence level I

PREFERRED RESPONSE ▶

DISCUSSION: Therapeutic studies investigate the results of treatment. Level 1 evidence includes randomized controlled trial with statistically significant difference or no statistically significant difference but narrow confidence interval

A level II therapeutic study would include a lesser-quality randomized controlled trial (eg, <80% follow-up, no blinding, or improper randomization). A non-randomized prospective cohort study that compares the results of treatment or systematic reviews of level II studies or level I studies with heterogenous results would also be considered a level II study.

Prognostic studies investigate the effect of a patient characteristic on the outcome of disease. Diagnostic studies investigate the efficacy of a diagnostic test. Illustration A is a table detailing the levels of evidence.

Illustrations: A

REFERENCES:

1. Bhandari M. Evidence-based orthopaedics. Issues in research design, analysis, and critical appraisal. In: Einhorn TA, O'Keefe RJ, Buckwalter JA, eds. Orthopaedic Basic Science: Foundations of Clinical Practice. 3rd ed. Rosemont, IL: American Academy of Orthopaedic Surgeons; 2007:87-101.

2. Kocher MS. Evaluation of the medical literature. In: Morrissy RT, Weinstein SL, eds. Lovell and Winter's Pediatric Orthopaedics. 6th ed. Philadelphia, PA: Lippincott Williams & Wilkins; 2006:97-112.

3. Moseley JB, O'Malley K, Petersen NJ, Menke TJ, Brody BA, Kuykendall DH, Hollingsworth JC, Ashton CM, Wray NP. A controlled trial of arthroscopic surgery for osteoarthritis of the knee. N Engl J Med. 2002 Jul 11;347(2):81-8. PMID: 12110735 (Link to Abstract)

Question Authors:

Michael Hughes MD, Ben Taylor MD, Dave Marcu MD,

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(OBQ10.242) Which of the following study designs represent a level III evidence study? Topic

Review Topic

1. Prospective, randomized controlled trial
2. Retrospective case-control study
3. Retrospective case series
4. Prospective cohort study
5. Expert opinion

PREFERRED RESPONSE ▶

DISCUSSION: The practice of evidence based medicine means integrating individual clinical expertise with the best available external clinical evidence from systematic research. Therapeutic study hierarchy of evidence has been established to better analyze studies in a reproducible fashion. Level I studies include well-designed randomized controlled prospective studies (RCT). Level II include lower quality designed prospective RCT as well as prospective cohort studies. Level III include retrospective cohort studies and case-control studies. Level IV include case series. Level V include case reports, expert opinion, and personal observation. This is summarized in illustration A. The referenced article by Brighton et al is a review of how the level of evidence has evolved and how the different levels can carry varied amounts of impact on clinical treatments and future research.

Illustrations: A

REFERENCES:

1. Bhandari M. Evidence-based orthopaedics: issues in research design, analysis, and critical appraisal. In: Einhorn TA, O’Keefe RJ, Buckwalter JA, eds. Orthopaedic Basic Science, 3 rd ed. Rosemont, IL: American Academy of Orthopaedic Surgeons; 2007:87-101.

2. Brighton B, Bhandari M, Tornetta P 3rd, Felson DT. Hierarchy of evidence: from case reports to randomized controlled trials. Clin Orthop Relat Res. 2003 Aug;(413):19-24. PMID:12897592 (Link to Abstract)

Question Authors:

Ben Taylor MD, Patrick McCulloch MD,

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(OBQ08.127) Using levels of evidence in research studies, which of the following represents a level II study? Topic

Review Topic

1. Retrospective case control study
2. Prospective cohort study
3. Case report of 3 patients with the same disease
4. High-quality randomized prospective clinical trial
5. The opinion of a review panel at the annual AAOS meeting

PREFERRED RESPONSE ▶

DISCUSSION: Level II Evidence includes prospective cohort studies. There are 5 levels of evidence in clinical research. Level I includes randomized clinical trials. Level II includes prospective cohort studies. Level III includes case control studies AND retrospective cohort studies. Level IV includes case series. Level V evidence includes expert opinion, case reports, and personal observation. The cited reference by Bernstein et al is an excellent review of Evidence Based Medicine (EBM) and describes the 5 step process of making medical decisions based on the available, and often limited, evidence. These steps include: 1) Formulate answerable questions. 2) Gather the evidence. 3) Appraise the evidence. 4) Implement the evidence. 5) Evaluate the process. The reference by Spindler et al is another review article that discusses the different levels of evidence for different study types.

REFERENCES:

1. Vaccaro, AR. (ED). Orthopaedic Knowledge Update 8. American Academy of Orthopaedic Surgeons. 2005

2. Bernstein J. Evidence-based medicine. J Am Acad Orthop Surg. 2004Mar-Apr;12(2):80-8. PMID:15089081 (Link to Abstract)

3. Spindler KP, Kuhn JE, Dunn W, Matthews CE, Harrell FE Jr, Dittus RS. Reading and reviewing the orthopaedic literature: a systematic, evidence-based medicine approach. J Am Acad Orthop Surg. 2005 Jul-Aug;13(4):220-9. PMID:16112979 (Link to Abstract)

Question Authors:

Patrick O'Donnell MD/PhD, Patrick McCulloch MD, John Badylak MD,

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Evidence & References Show References

Level of Evidence 1 (Randomized Control Trial)

Moseley JB, O'Malley K, Petersen NJ, Menke TJ, Brody BA, Kuykendall DH, Hollingsworth JC, Ashton CM, Wray NP. A controlled trial of arthroscopic surgery for osteoarthritis of the knee. N Engl J Med. 2002 Jul 11;347(2):81-8. PMID: 12110735 (Link to Abstract)

Level of Evidence 5 and Other Journal Articles (includes Case Reports, Expert Opinions, Personal Observations, and Biomechanic Studies)

Brighton B, Bhandari M, Tornetta P 3rd, Felson DT. Hierarchy of evidence: from case reports to randomized controlled trials. Clin Orthop Relat Res. 2003 Aug;(413):19-24. PMID:12897592 (Link to Abstract)

Textbooks

Review of Orthopaedics, 6th Edition, Mark D. Miller MD, Stephen R. Thompson MBBS MEd FRCSC, Jennifer Hart MPAS PA-C ATC, an imprint of Elsevier, Philadelphia, Copyright 2012
AAOS Comprehensive Orthopaedic Review, Jay R. Leiberman. Published by American Academy of Orthopaedic Surgeons, Rosemont IL. Copyright 2009
Orthopaedic Knowledge Update 10, John M Flyn. Published by American Academy of Orthopaedic Surgeons, Rosemont IL. Copyright 2011
Hoppenfeld SP. Surgical Exposures in Orthopaedics: The Anatomic Approach. Lipponcott, Williams, and Wilkins, Philadelphia, PA, Copyright 2009
Orthopaedic In-training Examination (OITE) Questions 2004-2012, American Academy of Orthopaedic Surgeons, Rosemont IL. Copyright 2004-2012
Self-Assessment Examination (SAE) Questions 2004-2012, American Academy of Orthopaedic Surgeons, Rosemont IL. Copyright 2004-2012
Bhandari M. Evidence-based orthopaedics. Issues in research design, analysis, and critical appraisal. In: Einhorn TA, O'Keefe RJ, Buckwalter JA, eds. Orthopaedic Basic Science: Foundations of Clinical Practice. 3rd ed. Rosemont, IL: American Academy of Orthopaedic Surgeons; 2007:87-101.
Kocher MS. Evaluation of the medical literature. In: Morrissy RT, Weinstein SL, eds. Lovell and Winter's Pediatric Orthopaedics. 6th ed. Philadelphia, PA: Lippincott Williams & Wilkins; 2006:97-112.
Bhandari M. Evidence-based orthopaedics: issues in research design, analysis, and critical appraisal. In: Einhorn TA, O’Keefe RJ, Buckwalter JA, eds. Orthopaedic Basic Science, 3 rd ed. Rosemont, IL: American Academy of Orthopaedic Surgeons; 2007:87-101.
Vaccaro, AR. (ED). Orthopaedic Knowledge Update 8. American Academy of Orthopaedic Surgeons. 2005

Undefined

Bhandari M. Evidence-based orthopaedics: issues in research design, analysis and critical appraisal. In: Einhorn TA, O’Keefe RJ, Buckwalter JA, eds. Orthopaedic Basic Science: Foundations of Clinical Practice. 3rd ed. Rosemont, IL: American Academy of Orthopaedic Surgeons; 2007:87-101
Wright J. Levels of evidence and grades of recommendations: An evaluation of literature leads to a common evaluation system. 2005. http://www2.aaos.org/aaos/archives/bulletin/apr05/fline9.asp (Last Accessed 8/2/2012).
Bernstein J. Evidence-based medicine. J Am Acad Orthop Surg. 2004Mar-Apr;12(2):80-8. PMID:15089081 (Link to Abstract)
Spindler KP, Kuhn JE, Dunn W, Matthews CE, Harrell FE Jr, Dittus RS. Reading and reviewing the orthopaedic literature: a systematic, evidence-based medicine approach. J Am Acad Orthop Surg. 2005 Jul-Aug;13(4):220-9. PMID:16112979 (Link to Abstract)

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Level of Evidence

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Evidence & References Show References

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