Table 2

Level of evidence base for clinical management recommendations: number by level of evidence as defined by US Agency for Health Care Policy and Research

Level A Level B Level C
Marfan syndrome21411
Total2  (2%)39  (32%)81  (66%)
  • Level A requires at least one RCT as part of a body of publications of overall good quality and consistency addressing specific recommendation (evidence levels 1a, 1b).

  • Level B requires the availability of well conducted clinical studies but no RCT on the topic of the recommendation (evidence levels 2a, 2b, 3).

  • Level C requires evidence obtained from expert committee reports or opinions/clinical experiences of respected authorities. Indicates an absence of directly applicable studies of good quality.