You 2006.
| Methods | RCT | |
| Participants | Country: China. 13 villages in Linqu County, Shandong Province. 2258 participants were randomly selected in villages and given baseline endoscopy. Mean age 46.8 (range 35 to 64) years, 50.0% men. Excluded participants who were too ill or who refused. Method to confirm H. pylori infection: serological testing 64% participants with preneoplastic lesions at baseline Study period: 1994‐2010 |
|
| Interventions | 1. Omeprazole 20 mg and amoxicillin 1 g twice daily for 2 weeks, with or without vitamin or garlic supplements (n = 1130). Participants who had continued evidence of infection after 3 months received a repeat course of treatment for 2 weeks unless they had previously developed rashes or other evidence of allergy to the initial treatment. 2. Placebo, with or without vitamin or garlic supplements (n = 1128)
2x2x2 factorial design: H. pylori eradication; dietary supplementation with capsules containing vitamin C, vitamin E, and selenium; dietary supplementation with capsules containing steam‐distilled garlic oil and Kyolic aged garlic extract. Garlic and vitamin supplements were not given in June and July 1999, and garlic supplements were not given in September 2002 because of interruptions in the availability of the supplement. Follow up: 14.7 years. |
|
| Outcomes | Gastric cancer: Histological examination, clinical, laboratory, or pathological data and cause‐specific mortality. Prevalence of dysplasia and other precancerous gastric lesions: prevalence of dysplasia or gastric cancer (score > 6); prevalence of severe chronic atrophic gastritis, intestinal metaplasia, dysplasia, or gastric cancer; and average severity score, effects of one‐time H. pylori treatment and long‐term vitamin or garlic supplements in reducing the prevalence of advanced precancerous gastric lesions. Secondary endpoints: rates of transition from baseline to final histopathologic states and the effects of treatments on these rates of transition; evidence of the effectiveness of amoxicillin and omeprazole in eradicating H. pylori; and blood pressure at the time of the final examination. |
|
| Notes | 1. You 2006a: no gastric cancer data for those who did not receive dietary supplement; some participants were ineligible after randomisation and were excluded in the main analyses, these were included in the sensitivity analyses. 2. Some data were obtained from the authors. 3. Inconsistent sample size between Gail 1998 protocol (3411 randomised = 2285 H. pylori‐positive and 1126 H. pylori‐negative); and 3365 randomised (2258 H. pylori‐positive vs 1107 H. pylori‐negative) in You 2006,. 4. Eradication rate: 73.2%. |
|
| Risk of bias | ||
| Bias | Authors' judgement | Support for judgement |
| Random sequence generation (selection bias) | Low risk | "We masked both the subjects and the researchers to treatment assignment. After confirming the eligibility of subjects, we assigned treatments randomly at Westat, Inc. in the United States and used this assignment to distribute coded bottles of capsules from the pharmacy in the city of Weifang in Shandong Province" |
| Allocation concealment (selection bias) | Low risk | Central randomisation, with distribution of coded bottles of capsules from the pharmacy. Pill bottles bearing codes corresponding to those assignments were then distributed to the study participants. |
| Blinding of participants and personnel (performance bias) All outcomes | Low risk | Look‐alike placebo capsules containing lactose and starch for amoxicillin and sucrose and starch for omeprazole were given to serologically positive controls and to all seronegative participants. To protect blinding, the investigators randomly selected an equal number of participants of the placebo arm from the same village and 10‐year age range for retreatment with placebo. Look‐alike placebo capsules were also used for supplements. |
| Blinding of outcome assessment (detection bias) All outcomes | Low risk | Outcome assessors were blinded, only 1 person had the authority to break the code when necessary (e.g. toxicity). |
| Incomplete outcome data (attrition bias) All outcomes | Low risk | 2285 H. pylori‐positive participants randomised in Gail 1998, 2258 H. pylori‐positive participants were analysed in You 2006. Overall, only 13% of participants did not have final gastric biopsy data. |
| Selective reporting (reporting bias) | Low risk | Reported prespecified outcomes, some data were obtained from the authors. |
| Other bias | Low risk | No other risk of bias was noted. |
GI: gastrointestinal ITT: intention‐to‐treat RCT: randomised controlled trial