Guide
© The Johns Hopkins Hospital/Johns Hopkins University. May not be used or reprinted without permission. Page 1
Evidence Levels
Quality Guides
Level I Experimental study, randomized controlled trial (RCT) Systematic review of RCTs, with or without meta-analysis
A High quality: Consistent, generalizable results; sufficient sample size for the study design; adequate control; definitive conclusions; consistent recommendations based on comprehensive literature review that includes thorough reference to scientific evidence
B Good quality: Reasonably consistent results; sufficient sample size for the study
design; some control, fairly definitive conclusions; reasonably consistent recommendations based on fairly comprehensive literature review that includes some reference to scientific evidence
C Low quality or major flaws: Little evidence with inconsistent results; insufficient
sample size for the study design; conclusions cannot be drawn
Level II Quasi-experimental study Systematic review of a combination of RCTs and quasi- experimental, or quasi-experimental studies only, with or without meta-analysis Level III Non-experimental study Systematic review of a combination of RCTs, quasi-experimental and non-experimental studies, or non-experimental studies only, with or without meta-analysis Qualitative study or systematic review with or without a meta- synthesis
Johns Hopkins Nursing Evidence-Based Practice Appendix C: Evidence Level and Quality Guide
© The Johns Hopkins Hospital/Johns Hopkins University. May not be used or reprinted without permission. Page 2
Evidence Levels
Quality Guides
Level IV Opinion of respected authorities and/or nationally recognized expert committees/consensus panels based on scientific evidence Includes: Clinical practice guidelines Consensus panels
A High quality: Material officially sponsored by a professional, public, private organization, or government agency; documentation of a systematic literature search strategy; consistent results with sufficient numbers of well-designed studies; criteria-based evaluation of overall scientific strength and quality of included studies and definitive conclusions; national expertise is clearly evident; developed or revised within the last 5 years
B Good quality: Material officially sponsored by a professional, public, private
organization, or government agency; reasonably thorough and appropriate systematic literature search strategy; reasonably consistent results, sufficient numbers of well-designed studies; evaluation of strengths and limitations of included studies with fairly definitive conclusions; national expertise is clearly evident; developed or revised within the last 5 years
C Low quality or major flaws: Material not sponsored by an official organization or
agency; undefined, poorly defined, or limited literature search strategy; no evaluation of strengths and limitations of included studies, insufficient evidence with inconsistent results, conclusions cannot be drawn; not revised within the last 5 years
Johns Hopkins Nursing Evidence-Based Practice Appendix C: Evidence Level and Quality Guide
© The Johns Hopkins Hospital/Johns Hopkins University. May not be used or reprinted without permission. Page 3
Level V Based on experiential and non-research evidence Includes: Literature reviews Quality improvement, program or financial evaluation Case reports Opinion of nationally recognized experts(s) based on
experiential evidence
Organizational Experience:
A High quality: Clear aims and objectives; consistent results across multiple settings; formal quality improvement, financial or program evaluation methods used; definitive conclusions; consistent recommendations with thorough reference to scientific evidence
B Good quality: Clear aims and objectives; consistent results in a single setting;
formal quality improvement or financial or program evaluation methods used; reasonably consistent recommendations with some reference to scientific evidence
C Low quality or major flaws: Unclear or missing aims and objectives; inconsistent
results; poorly defined quality improvement, financial or program evaluation methods; recommendations cannot be made
Literature Review, Expert Opinion, Case Report, Community Standard, Clinician Experience, Consumer Preference:
A High quality: Expertise is clearly evident; draws definitive conclusions; provides scientific rationale; thought leader(s) in the field
B Good quality: Expertise appears to be credible; draws fairly definitive conclusions;
provides logical argument for opinions C Low quality or major flaws: Expertise is not discernable or is dubious; conclusions