Risk of bias assessment: Randomised Controlled Trial (Cochrane risk of bias tool)
Random sequence generation
Describe the method used to generate the allocation sequence in sufficient detail to allow an assessment of whether it should produce comparable groups.
- drawn by individual randomisation
from the population registry
Not clear enough
Describe the method used to conceal the allocation sequence in sufficient detail to determine whether intervention allocations could have been foreseen in advance of or during, enrolment.
Describe all measures used, if any, to blind outcome assessors from knowledge of which intervention a participant received. Provide any information relating to whether the intended blinding was effective.
- Assessment of both the cause of death and colorectal cancer staging for the
registries used was blinded to the group status of participants in the study.
Unsure what this means
Incomplete outcome data
Describe the completeness of outcome data for each main outcome, including attrition and exlusions from the analysis. State whether attrition and exclusions were reported, the numbers in each intervention group (compared with total randomized participants), reasons for attrition/exclusions where reported, and any re-inclusions in analyses performed by the review authors.
- Attrition and exclusion well explained; numbers excluded in control group were higher than for screening group but had same reasons for exclusion.
Selective outcome reporting
State how the possibility of selective outcome reporting was examined by the review authors and what was found.
- Mortality pre-specified in protocol and methods
What was the risk of bias from selective outcome reporting? Assessments should be made for each main outcome (or class of outcomes).
Other sources of bias
Overall risk of bias
|Unclear risk of bias||Additional comments: Please replace this text and include any additional comments in regards to your risk of bias rating|
This appraisal has been completed.
- Hoff G, Grotmol T, Skovlund E, Bretthauer M, Norwegian Colorectal Cancer Prevention Study Group. Risk of colorectal cancer seven years after flexible sigmoidoscopy screening: randomised controlled trial. BMJ 2009 May 29;338:b1846 Abstract available at http://www.ncbi.nlm.nih.gov/pubmed/19483252.
- Assigned to
- Topic area
- Guidelines:Colorectal cancer
- Clinical question
- Form:Quality appraisal rct-cochrane
Section below only relevant for Cancer Council Project Officer