TABLE I.

Quality of evidence assessment and classification of recommendations as defined by the Canadian Task Force on Preventive Health Care

Quality of evidence assessment7		Classification of recommendations8
I	Evidence obtained from at least one properly randomized controlled trial	A	There is good evidence to recommend the clinical preventive action.
II-1	Evidence from well-designed controlled trials without randomization	B	There is fair evidence to recommend the clinical preventive action.
II-3	Evidence obtained from comparisons between times or places with or without the intervention (dramatic results in uncontrolled experiments—such as the results of treatment with penicillin in the 1940s—could also be included in the category)	D	There is fair evidence to recommend against the clinical preventive action.
III	Opinions of respected authorities, based on clinical experience, descriptive studies, or reports of expert committees	E	There is good evidence to recommend against the clinical preventive action.
		L	There is insufficient evidence (in quantity or quality) to make a recommendation; however, other factors could influence decision-making.