エビデンスのレベル(level)、エビデンスの階層構造(hierarchy)、エビデンスの質(quality)、などのEBM用語が現在も多用されていますが、
（GRADEシステムが登場する前は）エビデンスの質評価は研究デザインに依存したものでした。
そして、Oxford Centre for Evidence-based Medicine (OCEBM) – Levels of Evidenceの2011年new version（部分的にGRADEシステムを利用）のように、GRADEシステムが報告された後でも、多くのグループにおいてエビデンスの質の評価方法は変わっていません。
OCEBMを参考にしているMinds2007も同じ評価アプローチです。
いったい、いつから研究デザインによるエビデンス・レベルの評価が行われるようになったのだろうか？
・・・・・・・
その最初の報告論文は、1979年のCanadian Task Force on the Periodic Health Examinationで、David Sackettも名を連ねています。
periodic health examination. Canadian Task Force on the Periodic Health Examination CMAJ November 3, 1979 121:1193-1254
■Quality of the evidenceは4段階：
I: Evidence obtained from at least one properly randomized controlled trial.
II-1: Evidence obtained from well designed cohort or case-control analytic studies, preferably from
more than one centre or research group.
II-2: Evidence obtained from comparisons between times or places with or without the intervention.
Dramatic results in uncontrolled experiments (such as the results of the introduction of penicillin
in the 1 940s) could also be regarded as this type of evidence.
III: Opinions of respected authorities, based on clinical experience, descriptive studies or reports
of expert committees.
■Classification of recommendationsは5段階：
A: There is good evidence to support the recommendation that the condition be specifically considered
in a periodic health examination.
B: There is fair evidence to support the recommendation that the condition be specifically considered
in a periodic health examination.
C: There is poor evidence regarding the inclusion of the condition in a periodic health examination,
and recommendations may be made on other grounds.
D: There is fair evidence to support the recommendation that the condition be excluded from consideration in a periodic health examination.
E: There is good evidence to support the recommendation that the condition be excluded from consideration in a periodic health examination.
the final recommendation for each condition relied heavily on our assessment of the evidence for effectiveness of treatment. Thus, a class A recommendation was rarely made in the absence of grade I evidence regarding effectiveness of treatment or prevention. However, an exception to this rule occurred when a clinical intervention was shown, in grade II terms, to save the lives of victims of a previously universally fatal condition. For example, if malignant hypertension is left untreated, all affected patients will die; if treated, most will survive. Thus, grade II evidence is sufficient for a class A recommendation. Such examples are rare, however, and grade I evidence was required for the highest recommendation for most of the conditions.
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論文には、C recommendationの考え方とか、risk benefitバランス、sensitivity, secificity and predictive value; and the safety, simplicity, cost and acceptability to the patient.、など現在のGRADEにつながる基本理念が記載されています。
注： GRADEにおいては、個々の研究のエビデンスを評価するのではなく、複数の研究のシステマティック・レビューを使う。すなわち、アウトカムを主体として研究横断的に収集した総体エビデンス（body of evidence）の質を、アウトカムごとに評価する
