Scientific evidence is collected in many ways. This resource demonstrates the five Levels of Evidence to use while making educated determinations about prescribing and care.
- OPEN’s prescribing recommendations reference levels of evidence that were used to draw conclusions about opioid prescribing, so that providers can make educated determinations about prescribing and care.
- The levels of evidence complement each other and each level has benefits and challenges.
- Level 1 evidence is the most robust, however these studies require the most resources and it is not always possible to collect evidence at this level.
- Level 2 evidence and Level 3 evidence may be more feasible to conduct in real-world conditions.
- Level 4 evidence and Level 5 evidence come from expert opinions. This evidence is helpful in rare circumstances or when recommendations are needed before adequate data can be collected.
Level 1 – Randomized Controlled Trials
Level 1 studies are scientific studies in which subjects are randomly assigned a condition of the independent variable; the treatment groups are compared against a control group; all subjects are recruited from the same eligible population. These studies are often used to evaluate medication efficacy and treatment efficacy. These studies can only include prospective data.
- Experimental Designs
- Randomized Controlled Trials
- Mixed-Method Designs with Level 1 Quantitative Studies
- Systematic Review of Randomized Controlled Trials
Level 2 – Quasi-Experimental Studies
Level 2 studies are scientific studies in which subjects from the eligible population are assigned a non-random condition based on factors such as demographic data, previous treatments, or participant choice. These studies are often used to evaluate cause-and-effect relationships and interventions that cannot be randomized. These studies can include retroactive or prospective data.
- Quasi-Experimental Designs
- Mixed-Method Designs with Level II Quantitative Studies
- Systematic Review of Quasi-Experimental Studies and Randomized Controlled Trials
- Systematic Review of Quasi-Experimental Studies Only
Level 3 – Non-Experimental Studies
Level 3 studies are scientific studies in which a variable is observed and measured without being manipulated. These studies can be used to evaluate phenomena as they exist without intervention and aim to explain how a variable naturally exists. These studies can include retroactive or prospective data. These studies cannot be used to explore cause-and-effect relationships.
- Nonexperimental Designs
- Exploratory, Convergent, or Multiphasic Mixed Methods Studies
- Explanatory Mixed-Method Designs with Level III Quantitative Studies
- Systematic Review of Nonexperimental Studies
- Systematic Review of Randomized Controlled Trials, Nonexperimental Studies and Quasi-Experimental Studies
Level 4 – Research-Based Expert Consensus
Level 4 recommendations are based on the conclusions of multiple experts, such as those belonging to a committee, based on previous scientific research. This evidence can also include clinical practice guidelines that are followed by the majority of experts in the field.
- Opinion of Respected Authorities
- Clinical Practice Guidelines
- Opinion of Nationally-Recognized Expert Committees
- Consensus Panel Statements Based on Scientific Evidence
Level 5 – Experience-Based Expert Opinion
Level 5 recommendations are based on the opinions of individual experts based on their own professional experiences. This evidence can also include literature reviews of relevant studies, case reports, and institutional reviews of data.
- Experiential Research
- Non-research Evidence
- Integrative Reviews
- Literature Reviews
- Quality Improvement Evaluations
- Program Evaluations
- Financial Evaluations
- Case Reports
- Opinion of Nationally Recognized Expert Based on Experiential Evidence
- Burns PB, Rohrich RJ, Chung KC. The levels of evidence and their role in evidence-based medicine. Plast Reconstr Surg. 2011 Jul;128(1):305-310. doi: 10.1097/PRS.0b013e318219c171. PMID: 21701348; PMCID: PMC3124652.
- Johns Hopkins Nursing Evidence-Based Practice guide – https://libguides.ohsu.edu/ld.php?content_id=16277844
- Stony Brook University Evidence-Based Medicine guide – https://guides.library.stonybrook.edu/evidence-based-medicine/levels_of_evidence
- University of California Irvine Evidence-Based Medicine Subject Guide: EBM Pyramid – https://guides.lib.uci.edu/ebm/pyramid
Cite this work:
OPEN: Opioid Prescribing Engagement Network. (2022). Hierarchy of Evidence for Opioid Prescribing Recommendations. Retrieved from https://doi.org/10.56137/OPEN.000077