Quality of evidence (QoE) levels and source of evidence

IEvidence from at least one properly designed randomised, controlled trial;  with the primary objective of the study aligned with the recommendation being made.
IIEvidence from at least one well-designed clinical trial, without randomisation; from  cohort or case-controlled analytic studies (preferably from more than one centre);  from multiple time series; or from dramatic results of uncontrolled experiments.
 rMeta-analysis or systematic review of randomised control trial
 tTransferred evidence i.e. results from different patient cohorts, or similar  immune-status situation
 hComparator group: historical control
 uUncontrolled trials
 aPublished abstract presented at an international symposium or meeting
IIIEvidence from opinions of respected authorities, based on clinical experience,  descriptive case studies, or reports of expert committees.