Colorectal Cancer Screening in Average Risk Populations: Evidence Summary

Table 3

GRADE evidence profile—gFOBT versus no screening.

Quality assessment

Number of patients

Effect

Quality^1

Importance

Number of studies

Design

Risk of bias

Inconsistency

Indirectness

Imprecision

Other considerations

gFOBT (cases/person-years)

No screening (cases/person-years)

Relative; (95% CI)

Absolute; (cases/person-years)

CRC mortality (followup: range 17–30 years)

4

Randomised trials

Not serious

Not serious

Not serious

Not serious

Not serious

2027/2674854 (0.08%)

2326/2669246 (0.09%)

RR 0.87; (0.82 to 0.92)

113 fewer per 1000000 (from 70 fewer to 157 fewer)

⨁⨁⨁⨁; High

Critical

Control (gFOBT + FS) = 0.06%

78 fewer per 1000000 (from 48 fewer to 108 fewer)

Complications from tests (from Holme et al. 2013 [10])^2

3

Randomized trials

Not serious

Not serious

Not serious

Not serious

Not serious

N/A^3

⨁⨁⨁⨁; High

Critical

All-cause mortality (follow-up: range 17–30 years)

4

Randomized trials

Not serious

Not serious

Not serious

Not serious

Not serious

74,481/2,674,854 (2.8%)

74,174/2,669,246 (2.8%)

RR 1; (0.99 to 1.01)

0 fewer per 1,000,000 (from 278 fewer to 278 more)

⨁⨁⨁⨁; High

Important

Control (gFOBT + FS) = 1.85%

0 fewer per 1000000 (from 185 fewer to 185 more)

CRC incidence (follow-up: range 17–30 years)

5

Randomized trials

Not serious

Not serious

Serious^4

Not serious

Not serious

4324/2,434,487 (0.2%)

4489/2,431,961 (0.2%)

RR 0.96 (0.9 to 1.02)

74 fewer per 1,000,000 (from 37 more to 185 fewer)

⨁⨁⨁◯; Moderate

Important

Control (gFOBT + FS) = 0.16%

64 fewer per 1,000,000 (from 32 more to 160 fewer)

CI: confidence interval; CRC: colorectal cancer; FS: flexible sigmoidoscopy; gFOBT: guaiac fecal occult blood test; GRADE: Grading of Recommendations, Assessment, Development and Evaluations; ITS: intention to screen; N/A: not applicable; RR: relative risk.
In order to have comparable control rates across all gFOBT and FS trials, the control rates for the no screening groups in the gFOBT and FS trials were combined and calculated from the total number of cases across all gFOBT and FS trials over the total number of person-years across all gFOBT and FS trials.
¹GRADE working group grades of evidence:
(i) High quality: we are very confident that the true effect lies close to that of the estimate of effect.
(ii) Moderate quality: we are moderately confident in the effect estimate: the true effect is likely to be close to the estimate of the effect, but there is a possibility that it is substantially different.
(iii) Low quality: our confidence in the effect estimate is limited: the true effect may be substantially different from the estimate of the effect.
(iv) Very low quality: we have very little confidence in the effect estimate: The true effect is likely to be substantially different from the estimate of effect.
²Major complication defined as bleeding, perforation, or death within 30 days of screening, follow-up colonoscopy, or surgery.
³Holme et al. 2013 [10] reported a major complication rate of 0.03%.
⁴Goteborg trial used sigmoidoscopy and double-contrast barium enema as reference standard; other trials used colonoscopy.