Box 2: Criteria for levels of evidence in guideline recommendations*
LevelType of evidence
AAt least 2 consistent class I studies
BAt least 1 class I study or 2 consistent class II studies
CAt least 1 class II study or 2 consistent class III studies
Expert consensusConsensus among Canadian amyotrophic lateral sclerosis clinical experts where evidence meeting criteria for Level A through Level C is lacking
  • * See Box 1 for definitions of study classes.