Evidence-Based Practice for Nurses

Although the rating system in Figure 15-1 provides a commonly encountered

method for rating evidence, you will likely come across other useful rating

scales. Regardless of the scale selected, they all have in common ranking/

rating systems to stratify the evidence by quality. Several notable rating scales

are presented so that you can become familiar with alternative approaches.

Members of the Canadian Task Force on Preventive Health Care (CTFPHC)

were some of the first to generate levels of evidence (Centre for Evidence-Based

Medicine, 2013). The recommendations that typically accompany clinical

practice guidelines (CPGs) are graded by examining the risk versus the

benefit and the quality or strength of the evidence on which the information

is derived. Reviewers focus on decision making that supports evidence over

consensus. Current efforts of the CTFPHC center on preventive care and

health policy with guidelines generated for practitioners to use in clinical

practice (CTFPHC, 2016).

First convened by the U.S. Public Health Service in 1984, the U.S. Preven-

tive Services Task Force (USPSTF) adopted the CTFPHC methodology. The

USPSTF is currently sponsored by the Agency for Healthcare Research and

Quality (AHRQ). AHRQ’s mission is to improve the quality, safety, efficiency,

and effectiveness of health care for all Americans. AHRQ provides adminis-

trative, research, technical, and communication support for the USPSTF. The

USPSTF evaluates scientific studies related to clinical preventive services and

makes recommendations based on explicit criteria, generally intended for use

in preventive care and the primary care setting. Recommendations provide

information about the evidence, allowing clinicians to make informed practice

decisions. The USPSTF grades the strength of the evidence as “A” (strongly

recommends), “B” (recommends), “C” (no recommendation for or against),

“D” (recommends against), or “I” (insufficient evidence to recommend for

or against) while considering a balance of benefit and harm for the preven-

tive service (USPSTF, 2013). Recognizing the diversity of rating systems,

AHRQ identified three relevant domains and elements for systems to grade

the strength of the evidence (USPSTF, 2008).

1. Quality: The aggregate of quality rating for individual studies, predicted on
   the extent to which bias was minimized


2. Quantity: The magnitude of effect, numbers of studies, and sample size or
   power


3. Consistency: For any given topic, the extent to which similar findings are
   reported using similar and different study designs

AHRQ’s mission is to support quality of care and EBP, most notably through

its 11 Evidence-based Practice Centers (EPCs) throughout the United States.

The EPCs are awarded 5-year contracts to review relevant scientific materials

KEY TERM

levels of evidence:

Predetermined

scales that

guide decisions

for ranking

evidence; evidence

hierarchies

410 CHAPTER 15 Weighing In on the Evidence