Study design

Design:

randomised controlled trial (RCT) (NORwegian Colorectal CAncer Prevention [NORCCAP] trial 1). NCT00119912.

Allocation:

concealed.*

Blinding:

blinded (outcome assessors).*

Study question

Setting:

city of Oslo and Telemark County, Norway.

Participants:

55 736 people 55–64 years of age (mean 59 y, 50% women) who were included in a national population registry. People who died or had colorectal cancer before the study entry date were excluded, and those allocated to screening were included in the analysis but were not screened if they had prior open colorectal surgery, severe chronic cardiac or pulmonary disease, need for long-term care, cerebrovascular accident or hospital admission for coronary events in the past 3 months, were currently receiving lifelong anticoagulant therapy or cytotoxic therapy or radiotherapy for malignancy, or …