Evidence-Based Practice for Nurses

(Ben Green) #1
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

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