Question

What is meant when assessing the strength of evidence?

Answer 1

Strength of evidence means that the evidence is provided by a prospective, randomized controlled trial with masked outcome assessment, in a representative population.

It is mainly assessed to know whether the research will do more good than harm to the client.

Assessing the strength of evidence is vital for the following purposes;

• The quality of evidence across studies for each important outcome

• Which outcomes are critical to a decision

• The overall quality of evidence across these critical outcomes

• The balance between benefits and harms

• The strength of recommendations.

When assessing the Strength of evidence the following are noted;

• primary outcome is clearly defined
• exclusion/inclusion criteria are clearly defined
• relevant baseline characteristics are represented
• minimal potential for bias

Strength-of-Recommendation Taxonomy (SORT)

Code	Definition
A	Consistent, good-quality patient-oriented evidence *
B	Inconsistent or limited-quality patient-oriented evidence *
C	Consensus, disease-oriented evidence *, usual practice, expert opinion, or case series for studies of diagnosis, treatment, prevention, or screening

* Patient-oriented evidence measures outcomes that matter to patients: morbidity, mortality, symptom improvement, cost reduction, and quality of life. Disease-oriented evidence measures immediate, physiologic, or surrogate end points that may or may not reflect improvements in patient outcomes (e.g. blood pressure, blood chemistry, physiologic function, pathologic findings).

Types of research designs:

• Meta-analysis: A statistical analysis that combines or integrates the results of several independent clinical trials considered by the analyst to be "combinable" usually to the level of re-analyzing the original data; also sometimes called pooling or quantitative synthesis.

• Systematic review: A review of a body of data that uses explicit methods to locate primary studies, and explicit criteria to assess their quality.

• Randomized Controlled Trials: Individuals are randomly allocated to a control group and a group who receive a specific intervention. Otherwise the two groups are identical for any significant variables. They are followed up for specific end points.

• Cohort Studies: Groups of people are selected on the basis of their exposure to a particular agent and followed up for specific outcomes.

• Case Control Studies: Patients ("cases") with the condition are matched with "controls" without, and a retrospective analysis is used to look for differences between the two groups.

• Case Study: A report based on a single patient or subject; sometimes collected together into a short series.

• Expert Opinion and Anecdotal: A consensus of experience from the good and the great. Ex: Something someone told you after a meeting.

An evidence pyramid is a visual representation study designs organized by strength of evidence. Study designs and publications shown at the top of the pyramid are considered thought to have a higher level of evidence than designs or publication types in the lower levels of the pyramid.

Strength of evidence is based on research design. The most scientific, rigorous study designs are randomized controlled trials, systematic reviews, and meta-analysis. These types of studies are thought to provide stronger levels of evidence because they reduce, but do not eliminate, potential biases and confounders. Bias is " systematic error, or deviation from the truth, in results or inferences.

Confounding factors have "an effect on the dependent variable (and hence the outcome) that cannot be distinguished from the effect of the independent variable. This may lead to erroneous conclusions being drawn from the results of the experiment."

The quality of evidence indicates the extent to which one can be confident that an estimate of effect is correct. The strength of a recommendation indicates the extent to which one can be confident that adherence to the recommendation will do more good than harm.

Evidence-based practice involves tracking down the available evidence, assessing its validity, and then using the "best" evidence to inform decisions regarding care. Rules of evidence have been established to grade evidence according to its strength. Systematic reviews and RCTs represent the highest levels of evidence, whereas case reports and expert opinion are the lowest. This "ladder of evidence" was developed to a large extent for questions related to interventions or therapy.