Recommendation grades (A-I) and levels of evidence (I, II-1, II-2, II-3, III; good, fair, poor) are indicated after each recommendation. Definitions for these grades and levels are provided following the recommendations.
The Canadian Task Force on Preventive Health Care concludes that the existing evidence is conflicting and does not allow the task force to make a recommendation for or against the use of back belts to either prevent occupational low-back pain or to reduce lost work time due to occupational low-back pain (grade C recommendation) (Walsh & Schwartz 1990 [I, fair]; van Poppel et al. 1998 [I, fair]; Alexander et al. 1995 [I, fair]; Kraus et al. 2002 [I, fair]; Wassell et al. 2000 [II-2, good]).
Levels of Evidence - Research Design Rating
I Evidence from randomized controlled trial(s)
II-1 Evidence from controlled trial(s) without randomization
II-2 Evidence from cohort or case-control analytic studies, preferably from more than one centre or research group
II-3 Evidence from comparisons between times or places with or without the intervention; dramatic results in uncontrolled experiments could be included here
III Opinions of respected authorities, based on clinical experience; descriptive studies or reports of expert committees
Levels of Evidence - Quality (Internal Validity) Rating
Good A study (including meta-analyses or systematic reviews) that meets all design-specific criteria* well
Fair A study (including meta-analyses or systematic reviews) that does not meet (or it is not clear that it meets) at least one design-specific criterion* but has no known "fatal flaw"
Poor A study (including meta-analyses or systematic reviews) that has at least one design-specific* "fatal flaw," or an accumulation of lesser flaws to the extent that the results of the study are not deemed able to inform recommendations
*General design-specific criteria are outlined in Harris RP, Helfand M, Woolf SH, Lohr KN, Mulrow CD, Teutsch SM, Atkins D. Current Methods of the U.S. Preventive Services Task Force: A Review of the Process. Am J Prev Med. 2001;20(suppl 3):21-35.
Recommendations Grades for Specific Clinical Preventive Actions
A The CTF concludes that there is good evidence to recommend the clinical preventive action.
B The CTF concludes that there is fair evidence to recommend the clinical preventive action.
C The CTF concludes that the existing evidence is conflicting and does not allow making a recommendation for or against use of the clinical preventive action, however other factors may influence decision-making.
D The CTF concludes that there is fair evidence to recommend against the clinical preventive action.
E The CTF concludes that there is good evidence to recommend against the clinical preventive action.
I The CTF concludes that there is insufficient evidence (in quantity and/or quality) to make a recommendation, however other factors may influence decision-making.
