Group-level estimates
The effect sizes and comparisons presented in this database are group-level estimates derived from meta-analyses and randomized controlled trials. These estimates represent average effects across populations and do not necessarily reflect individual responses to treatment. Individual patients may experience outcomes that differ significantly from the average, depending on their unique characteristics, genetics, comorbidities, and other factors. Clinical decisions should always consider individual patient circumstances.
Meta-analysis limitations
While meta-analyses are powerful tools for synthesizing evidence across multiple studies, they have inherent limitations. The quality of a meta-analysis depends on the quality of the included studies. Meta-analyses can be affected by:
- Publication bias: studies with positive results are more likely to be published
- Heterogeneity: differences in study populations, methods, and interventions
- Study quality: methodological flaws in individual studies
- Reporting biases: selective reporting of outcomes or analyses
- Time lag: meta-analyses may not include the most recent research
The GRADE system (described below) is intended to be an indicator of these potential biases and help users assess the reliability of the evidence.
GRADE informs on what estimates are most reliable
To address the limitations described above, the GRADE (Grading of Recommendations, Assessment, Development and Evaluations) system is used throughout this database to indicate the certainty of evidence for each comparison. GRADE ratings help users understand which estimates are most reliable:
- High certainty: we are very confident that the true effect lies close to the estimate
- Moderate certainty: we are moderately confident in the effect estimate
- Low certainty: our confidence in the effect estimate is limited
- Very low certainty: we have very little confidence in the effect estimate
Higher GRADE ratings indicate more reliable evidence. When available, interventions with higher certainty evidence should generally be preferred, all other factors being equal. Pay close attention to GRADE ratings when using the preference tool or interpreting the database.
Not a medical device
This tool is intended for informational purposes only and is not a medical device. It does not diagnose, treat, or replace professional medical advice. Its use should be guided by a qualified healthcare provider in consultation with people with lived experience and their families. Clinical decisions should be made based on professional judgment and individual patient needs. This tool serves as a supplementary resource and should not be relied upon as a substitute for medical expertise.
The preference tool and intervention rankings are designed to support shared decision-making between clinicians and patients, but they cannot account for all relevant clinical factors. Always consult with a qualified healthcare professional before making treatment decisions.