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. 2017 Jan 8;2017(1):CD003430. doi: 10.1002/14651858.CD003430.pub2

Decosse 1989.

Methods Allocation: randomly assigned based on a table of random numbers
 Blindness: quote: "Only the pharmacist and the statistician knew the treatment allocations. One patient, a nurse, obtained a chemical analysis of her placebo capsule; all other patients and investigators remained blinded." (p.1291)
 Duration: 4 years
Setting: USA
Participants Inclusion criteria: adults with familial adenomatous polyposis; each of these participants had had a total colectomy and ileorectal anastomosis at least 1 year before entry into the trial
 Exclusion criteria: not stated
N = 62. (4 participants withdrew from the study early)
Sex: % male 36.2
Age: mean (Group 1/Group 2/Group 3) 35.2/31.0/34.7 years
 Baseline dietary fibre intake g/d: not reported
 Baseline characteristics similar for each group: no, the gender distribution was not similar
Interventions

  1. Low‐fibre supplement (2.2 g/d) + placebo. N = 22

  2. Low‐fibre supplement (2.2 g/d) + ascorbic acid (4 g/d) and alpha‐tocopherol (400 mg/d). N = 16

  3. High‐fibre supplement (22.5 g/d) + ascorbic acid (4 g/d) and alpha‐tocopherol (400 mg/d). N = 20
Outcomes Unable to use:
Adverse events (no adverse symptoms or findings could be attributed to the treatment agents)
Compliance
Dietary analysis
Polyp number ratios
Notes This study was supported by Public Health Service grants CA‐31711 and CA‐43601 from the National Cancer Institute, National Institutes of Health, Department of Health and Human Services
Risk of bias
Bias Authors' judgement Support for judgement
Random sequence generation (selection bias) Low risk Participants were randomly assigned based on a table of random numbers.
Allocation concealment (selection bias) Unclear risk No details
Blinding (performance bias and detection bias) 
 All outcomes Low risk "Only the pharmacist and the statistician knew the treatment allocations. One patient, a nurse, obtained a chemical analysis of her placebo capsule; all other patients and investigators remained blinded." (p.1291)
Blinding of outcome assessment (detection bias) 
 All outcomes Unclear risk No details
Incomplete outcome data (attrition bias) 
 All outcomes Low risk 4 participants withdrew from the study early. ITT analysis was used.
Selective reporting (reporting bias) Low risk All measured outcomes were reported.
Other bias Unclear risk No details