Interpretation of Evidence

Evidence-based practice requires the retrieval and a critical appraisal of the best available evidence. All sources used in the development of the certification program should be cited and the level of evidence provided. For example, “no observable difference occurs when 0.9% normal saline is used compared with heparinized solutions for maintaining catheter patency and functionality of arterial lines” (Cochrane Database of Systematic Reviews, 2014ᴸᴼᴱ¹).

Table 2: Levels of Evidence

Level I	Evidence obtained from a meta-analysis or systematic review of all relevant Randomized Controlled Trials (RCTs) or evidence-based clinical practice guidelines based on systemic reviews of RCTs or three or more RCTs of good quality that have similar results.
Level II	Evidence obtained from at least one well-designed RCT. (E.g., a large, multi-site RCT).
Level III	Evidence obtained from well-designed controlled trials without randomization. (I.e., quasi-experimental).
Level IV	Evidence obtained from well-designed case-control or cohort studies.
Level V	Evidence obtained from, systematic reviews of descriptive and qualitative studies (meta-synthesis).
Level VI	Evidence obtained from a single descriptive or qualitative study.
Level VII	Evidence obtained from the opinion of authorities and/or report of expert committees.

This level of effectiveness rating scheme is based on the following: Ackley, B. J., Swan, B. A., Ladwig, G., & Tucker, S. (2008). Evidence-based nursing care guidelines: Medical-surgical interventions. (p. 7). St. Louis, MO: Mosby Elsevier.