Hansen 1994.

Methods	Aim of study: to evaluate the efficacy of NAC with amoxacillin in people with H pylori associated gastritis. Study design: randomised, double‐blind. Study grouping: parallel group. Unit of allocation: by individuals. Country: Denmark. Start date: October 1989. End date: December 1990. Duration of participation: 25 weeks. Ethical approval: approved by regional ethics committee.
Participants	Total number randomised: 93. Method of recruitment: consecutive participants. Informed consent obtained: participants consented participation. Baseline imbalances: not reported. Withdrawals and exclusions: eleven excluded by non‐compliance, five because of side effects, three decided not to participate, four were withdrawn for other reasons. Subgroups measured: not reported. Subgroups reported: not reported. Mean age: 58 years. Gender (M/F): (42/28). Race/ethnicity: not reported. Severity of condition: not available in report. Comorbidities: not reported. Diagnostic criteria: positive test for H pylori either by histology, urease test or culture. Setting: not reported. Inclusion criteria: participants referred to gastroscopy because of dyspepsia with positive test for H pylori either by histology, urease test or culture. Exclusion criteria: participants with peptic ulcers, decreased renal function, treatment with colloidal bismuth subcitrate or antibiotics ‐ ongoing or within the last month, ongoing treatment with potential ulcer provoking or mucosa irritating medication such as steroids, NSAIDs and salicylates.
Interventions	Number randomised in each group: group A (n = 35) group B (n = 35). Dose: Group A: amoxacillin 375 mg three times a day and placebo three times a day. Group B: amoxacillin 375 mg three times a day and N‐acetylcysteine 600 mg three times a day. Duration of treatment period: 28 days. Timing: as described above. Delivery: not reported. Providers: not reported. Cointerventions: not reported. Economic information: not reported. Resource requirements: not reported. Integrity of delivery: not reported. Compliance: measured by pill count. Eleven participants failed to take treatment as planned and were removed from analysis.
Outcomes	Primary outcomes: eradication rates, defined as the number of participants with negative histology, culture and rapid urease test six months after treatment. Secondary outcomes: none. Time points measured and reported: immediately after treatment and six months after treatment. Person measuring/reporting: not reported. Unit of measurement: not reported. Scales: not reported. Imputation of missing data: not reported. Assumed risk estimates: not reported. Power: not reported.
Notes	Publication status: full text. Funding source: Astra Group A/S provided NAC and placebo. Conflict of interest: not reported. Contact with authors: we contacted the authors on 26 January 2017 and got no answer.
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Unclear risk	Comment: insufficient information to allow judgement.
Allocation concealment (selection bias)	Unclear risk	Comment: insufficient information to allow judgement.
Blinding of participants and personnel (performance bias) Eradication (frequency)	Low risk	Quote: "This study was designed as a prospective, randomised, double‐blind, placebo‐controlled trial" Comment: the authors stated that placebo was used in control group.
Blinding of participants and personnel (performance bias) Gastrintestinal adverse events	Unclear risk	Comment: the study did not address this outcome.
Blinding of participants and personnel (performance bias) Allergic adverse events	Unclear risk	Comment: the study did not address this outcome.
Blinding of participants and personnel (performance bias) Toxic adverse events	Unclear risk	Comment: the study did not address this outcome.
Blinding of outcome assessment (detection bias) Eradication (frequency)	Low risk	Comment: blinding unlikely to introduce bias provided the outcome was assessed by objective test.
Blinding of outcome assessment (detection bias) Gastrintestinal adverse events	Unclear risk	Comment: the study did not address this outcome.
Blinding of outcome assessment (detection bias) Allergic adverse events	Unclear risk	Comment: the study did not address this outcome.
Blinding of outcome assessment (detection bias) Toxic adverse events	Unclear risk	Comment: the study did not address this outcome.
Incomplete outcome data (attrition bias) Eradication (frequency)	High risk	Comment: there were 24.7% of participants lost to follow up. Reasons were provided but no information about balance between groups or the methods used for data imputation were given. This fact could substantially influence the results.
Incomplete outcome data (attrition bias) Gastrintestinal adverse events	High risk	Comment: there were 24.7% of participants lost to follow up. Reasons were provided but no information about balance between groups or the methods used for data imputation were given. This fact could substantially influence the results.
Incomplete outcome data (attrition bias) Allergic adverse events	High risk	Comment: there were 24.7% of participants lost to follow up. Reasons were provided but no information about balance between groups or the methods used for data imputation were given. This fact could substantially influence the results.
Incomplete outcome data (attrition bias) Toxic adverse events	High risk	Comment: there were 24.7% of participants lost to follow up. Reasons were provided but no information about balance between groups or the methods used for data imputation were given. This fact could substantially influence the results.
Selective reporting (reporting bias)	Low risk	Outcomes reported in methods were measured and analysed.
Other bias	Unclear risk	Astra Group provided NAC and placebo.