Bachh 2007.

Methods	Randomised, single‐blind, placebo‐controlled, parallel, single‐centre. Follow‐up 12 months, although treatment given for only 4 months
Participants	100 outpatients with smoking‐related COPD. Age > 50 years; post‐bronchodilator FEV₁ 30% to 80% predicted; reversibility < 12%; FEV₁/FVC < 70%. Stable medications and ICS permitted at steady dose Exclusions: intolerance of NAC, continuous treatment with OCS, NAC for 3/12 or more, asthma or atopy, other respiratory diseases, NYHA Class II or greater heart failure. Non‐compliance in taking medication Mean age: 61 (SD 7) years; 78% male. Mean duration of disease 6.4 years. Mean number of exacerbations in 2 years before study, 4.7. Mean FEV₁ 52% (SD 10) predicted and reversibility 6% (SD3). 18/100 (18%) were using ICS No dropouts recorded
Interventions	NAC 600 mg once daily or placebo for 4 months
Outcomes	Exacerbations, hospital admissions, pulmonary function tests, adverse effects
Notes	Indian study
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Unclear risk	Information not available
Allocation concealment (selection bias)	High risk	Single‐blind
Blinding of participants and personnel (performance bias) All outcomes	High risk	Single‐blind; investigators not blinded
Blinding of outcome assessment (detection bias) All outcomes	High risk	Single‐blind
Incomplete outcome data (attrition bias) All outcomes	Low risk	No dropouts recorded
Selective reporting (reporting bias)	Low risk	Main outcomes reported