with clarifying the steps of conducting integrative reviews in nursing. Ganong’s
article provided a grid layout that many find useful as a tool to track and compile
data from various research papers. Components of the grid include methods,
theories, and empirical findings of the reviewed papers. These grids are often
included in published integrative reviews. Whittemore (2005) noted that an
advantage to integrative reviews “is the ability to combine data from different
types of research designs and include theoretical, as well as, empirical literature”
(p. 57). In other words, integrative reviews do not need to include works that
use the same designs or research methods.
Meta-Analyses
Meta-analyses combine results of studies into a measurable format and statisti-
cally estimate the effects of proposed interventions. Often, individual studies
about an intervention fail to show statistical significance. But when the results
from multiple studies are combined in one large analysis, results may show that
the intervention is beneficial (Choi & Lam, 2016). For example, suppose there
are 10 studies about the effect of yoga on blood pressure, but none of the studies
showed that yoga reduced blood pressure. However, when the results are pooled,
data analysis showed statistical significance; then, it could be concluded that
yoga can reduce blood pressure. Unlike in an integrative review, meta-analyses
include works that are similar or identical so that statistical comparisons can
be made. Another difference between these two types of reviews is that meta-
analyses include both published and unpublished works. Evans and Kowanko
(2000) surmised that meta-analysis reviews grew from narrative reviews when
the increasing amounts of numerical data grew too cumbersome. According to
Whittemore (2005), meta-analyses are especially useful as sources of evidence
when large randomized trials are not feasible.
Systematic Reviews
Systematic reviews combine elements of the three previously discussed meth-
ods. These are “scientific tools which are used to summarize and communicate
the results and implications of otherwise unmanageable quantities of research”
(Evans & Kowanko, 2000, p. 35). Articles included in systematic reviews all
address the same clinical problem. “A well-specified clinical question, use of
the best available evidence, explicit methods, and an exhaustive search for
relevant primary studies are hallmarks of this method” (Whittemore, 2005,
p. 58). Systematic reviews adhere to strict eligibility criteria so that bias can
be minimized and reliable conclusions can be made (Higgins & Green, 2011).
Systematic reviews, combined with other types of guidelines, are sources that
can be helpful in situations when evidence is needed quickly. A brief editorial
by Cowell (2012) provides a comparative overview of these types of reviews as
well as ways in which to assess the quality of such reviews.
KEY TERMS
meta-analyses:
A scholarly paper
that combines
results of studies,
both published and
unpublished, into a
measurable format
and statistically
estimates the
effects of proposed
interventions
systematic
reviews: Rigorous
and systematic
syntheses of
research findings
about a clinical
problem4.2 Types of Evidence 101