To assess the impact of the meta-analysis methods, we also calculated summary RRs using fixed-effects model techniques, that is, the inverse variance and Mantel-Haenszel methods. Because the data were expected to be heterogeneous, extensive subgroup analysis was performed using the following moderator variables: (1) patient symptoms (some studies included only asymptomatic screening individuals, whereas others included symptomatic patients [eg, diarrhea and hematochezia] undergoing diagnostic colonoscopy); (2) study design (in some studies, colonoscopy was performed on all patients regardless of distal findings [“universal colonoscopy” design], whereas in others, patients first underwent FS, with colonoscopy performed only in those found to have distal polyps of any type [“nonuniversal colonoscopy” design]; in the latter group, biopsy of the distal polyp was often not performed until the time of colonoscopy); (3) publication date (studies were stratified according to whether they were published after 1992 [this date was chosen because a preliminary review showed that approximately half the studies were published after 1992]); (4) sample size (studies were stratified according to whether they enrolled >300 total patients); (5) demarcation definition (some studies defined the demarcation between the proximal and distal colon as the splenic flexure or the descending sigmoid junction, whereas others defined it as the extent of FS); (6) distal polyp size (some studies restricted themselves to subjects with distal polyps <5 mm, whereas others had no size restrictions); (7) age (some studies restricted participants to those ≥50 years); (8) family history (some studies included individuals with a family history of CRC, some excluded such patients, and others did not comment on family history); and (9) study quality. Unlike randomized controlled trials, observational studies do not have commonly used and well-validated quality scoring systems.13 Therefore, we created a simple scoring system for this meta-analysis. We assigned each study a score based on the type of publication (full article vs abstract), patient symptoms, study design, comparison groups, and sample size. Studies that were published in full, that included only asymptomatic screening patients, that featured a universal colonoscopy design, that included all 3 comparison groups, and that had 300 or more participants received 1 point for each category (for a maximum score of 5). Studies that were published as abstracts, that included symptomatic patients, that featured a nonuniversal colonoscopy design, that included only 2 of the 3 comparison groups, and that had fewer than 300 participants received 0 points for each category (for a minimum score of 0). Studies with low scores (0, 1, 2, or 3) were compared with studies with high scores (4 or 5). Because this meta-analysis included only published studies, we explored the possibility of publication bias by performing an inverted funnel plot analysis.