Key Steps in Infusing Evidence into CE Course Content: Step 2
Assessing the Evidence
Systematic Reviews
There are at least two important factors to keep in mind when assessing a systematic review.
- Relevance of the review to the specific topic
For example, if the presentation topic is treatment of teenagers with autism, of what relevance are reviews based primarily on studies of younger children? It is the presenter's responsibility to vet these reviews with the specific needs of the audience in mind. - Who wrote and published the review
While many reviews are produced by academic institutions and interdisciplinary collaborations, others are produced by advocacy groups or payors. It is important to consider who produced the reviews and to what extent they would likely be affected by positive or negative findings. However, reviews emanating from a "trusted" source are no more guaranteed to be of high quality than are reviews coming from a less objective source guaranteed to be flawed.
Individual Studies
Publication of a study in a peer-reviewed scientific journal is not a guarantee of quality. Individual studies are generally assessed along two dimensions: level of evidence and study quality. Level of evidence refers to the establishment of a hierarchy of study designs based on the ability of the design to protect against bias. Although there is no one universally accepted hierarchy, randomized controlled trials (RCTs) are considered to be the design least susceptible to bias, and various hierarchies follow from there through observational studies and non-experimental designs. The table below is one example of a hierarchy of levels of evidence.
SIGN Grading System 1999–2012
Levels of Evidence
| 1++ | High quality meta-analyses, systematic reviews of RCTs, or RCTs with a very low risk of bias |
| 1+ | Well-conducted meta-analyses, systematic reviews, or RCTs with a low risk of bias |
| 1- | Meta-analyses, systematic reviews, or RCTs with a high risk of bias |
| 2++ |
High quality systematic reviews of case control or cohort or studies |
| 2+ | Well-conducted case control or cohort studies with a low risk of confounding or bias and a moderate probability that the relationship is causal |
| 2- | Case control or cohort studies with a high risk of confounding or bias and a significant risk that the relationship is not causal |
| 3 | Non-analytic studies, e.g. case reports, case series |
| 4 | Expert opinion |
Adapted from the Scottish Intercollegiate Guidelines Network.
Study quality is an assessment of the extent to which a study, of whatever design, was designed and implemented appropriately. Again, there is no single universally accepted set of criteria for what constitutes a high quality study. For examples of study quality criteria, see the Scottish Intercollegiate Guidelines Network.
Expert Opinion
Expert Opinion Statements come from three areas:
- Guidelines: If recommendations are used, attribution should be given to the guideline developer in the recommendation statement.
Expert opinion can also be subjective statements or commentary with supporting reference(s).
- Clinical or professional practice recommendations from current ASHA Policy Documents provided that the recommendation was created as part of a consensus-based process.
- ASHA working group recommendations and recommendations of Working Groups of which ASHA is part such as JCIH, provided that the recommendation was created as part of a consensus-based process.
Source: ASHA Practice Portal statement on the use of evidence
Client/Patient/Caregiver Values
The examination of outcomes measures is recommended when describing client/patient/caregiver values to reflect the interests, values, needs and choices of the individuals served.
