Levels of evidence for clinical recommendations in the guideline:
Levels of evidence are used to guide the reader as to the strength of each individual recommendation. There are many documented approaches to grading levels of evidence in clinical guidelines. Some emphasize the quality of randomized clinical trials. However, because so few randomized clinical trials have studied pediatric concussion, we employed a broader system to rank evidence that also emphasizes the strength of meta-analyses or large, high-quality studies that may not involve interventions. In our system, is the strongest level of evidence.
A = Consistent, good-quality, patient-oriented evidence (example: at least one large randomized control trial, meta-analysis or systematic review with homogeneity, or large, high-quality, multi-centre cohort study);
B = Inconsistent or limited-quality patient-oriented evidence (example: smaller cohort studies, case studies or control trials with limitations);
C = Consensus, usual practice, opinion or weaker-level evidence