Levels of Evidence on SCIRE Community
SCIRE Professional uses a scale to rate evidence into six categories based on the type of study design and the quality and number of randomized controlled trials. This is explained in detail in the “SCIRE Systematic Review Process: Evidence” Chapter. On SCIRE Community, we have combined these levels into three categories:
Strong evidence is research evidence based on two or more high quality randomized controlled trials (SCIRE Professional Level 1a).
When there is strong evidence to support the use of a treatment, we can be confident that it has been proven to work. Likewise, if there is strong evidence that a treatment is ineffective, we can be confident that it does not work. In general, the more studies there are that have the same findings, the more confident we can be that a conclusion is accurate.
Moderate evidence is research evidence that is based on one randomized controlled trial, or one or more prospective controlled trials or cohort studies (SCIRE Professional Level 1b and 2).
When there is moderate evidence to support the use of a treatment, we have some guidance on whether a treatment works, but cannot be completely confident in its findings. More research is needed to be sure.
Weak evidence is based on lower level non-experimental study designs (like case studies and observational studies) or clinical consensus (SCIRE Professional Level 3, 4, and 5). These study designs are most susceptible to biases and errors so they are considered lower quality evidence when weighing treatment options. However, these studies often have different purposes, such as communicating unique and uncommon findings or making connections between different factors.
That being said, when we are trying to decide whether a treatment is effective, weak evidence provides early support that a treatment is effective or ineffective, but is not enough to draw conclusions from. More research is needed.
Other Categories of Evidence
Conflicting evidence is when some studies support the use of the treatment, and others do not. Conflicting evidence can be challenging to interpret, requiring careful assessment of the involved studies to determine potential problems or errors that could affect their results. Depending on the situation, conflicting evidence often makes it difficult to draw conclusions about whether a treatment works or not.
Expert opinion is a form of evidence based on the opinions of experts in the field. This includes the advice of health providers and researchers, and clinical consensus statements that are not based on research studies. Expert opinion is based on clinical experience or reasoning based foundational medical principles. Clinical reasoning has an important place in interpreting research evidence and making decisions when no high quality research has been done, expert opinion is considered a weak form of evidence compared to research evidence.
Making Decisions Using Research Evidence
Keep in mind that these broad levels are used to approximate the strength of evidence for ease of use and understanding. However, each category will vary somewhat and it is important to interpret this in the context of other important information. On top of the conclusions drawn from research evidence, other factors like potential risks, cost concerns, personal suitability, and your preferences also need to be taken into account when deciding on treatment options for your health.