Patient demographics, baseline and study characteristics
| Study [ref.], year | Study characteristics | Duration of study months | Patients (completed study visits) | NAC (daily dose) mg | Disease characteristics | Average age years | Male % | Current smokers % | Smoking history pack-years | ICS treatment % | Post-bronchodilator FEV1 % predicted | Jadad score |
| Zheng et al. [1], 2014 | Multicentre, prospective, randomised, double-blind, placebo-controlled, parallel groups | 12 | 964 | 1200 | COPD diagnosis using PFT, GOLD II–IV | 66.3 | 81.9 | 17.8 | 36.2 | 44.0 | 48.9 | 4 |
| Tse et al. [20], 2013 | Double-blind, randomised placebo-controlled | 12 | 108 | 1200 | COPD diagnosis using PFT, GOLD I–IV | 70.9 | 93.3 | 23.3 | NA | 79.0 | 59.6 | 4 |
| Schermer et al. [26], 2009 | Double blind, randomised, double dummy, placebo-controlled | 36 | 108 | 600 | COPD diagnosis using PFT, GOLD I–IV, chronic bronchitis | 59.4 | 72.9 | 53.6 | 27.3 | 49.0 | 69.8 | 4 |
| Bachh et al. [27], 2007 | Single blind, randomised, placebo-controlled study | 4 | 100 | 600 | COPD diagnosis using PFT, GOLD II and III | 61.4 | 78.0 | NA | 44.1 | 18.0 | 51.7 | 1 |
| Decramer et al. [3], 2005 | Double-blind, randomised, placebo-controlled, parallel groups | 36 | 354 | 600 | COPD diagnosis using PFT, GOLD II and III | 62.0 | 77.0 | 44.0 | NA | 70.0 | 57.0 | 4 |
| Gerrits et al. [29], 2003 | Retrospective cohort investigation | 12 | 1219 | From 200 to >600 | ICD-9: 491, 492, 496 | >55 | 59.6 | NA | NA | 35.9 | NA | NA |
| Pela et al. [24], 1999 | Open, randomised, controlled | 6 | 167 | 600 | COPD diagnosis using PFT and ATS/ERS criteria, FEV1 <70% pred | 66.0 | 75.7 | 24.0 | NA | 39.6 | 58.1 | 2 |
| Hansen et al. [19], 1994 | Multicentre, double-blind, randomised placebo-controlled, parallel groups | 5.5 | 129 | 1200 | Chronic bronchitis, FEV1 >50% pred | 51.4 | 43.1 | 92.2 | NA | NA | NA | 4 |
| Rasmussen and Glennow [25], 1988 | Multicentre, double-blind, randomised placebo-controlled, parallel groups | 6 | 91 | 600 | Chronic bronchitis | 58.8 | 56.9 | NA | NA | NA | NA | 4 |
| McGavin et al. [22], 1985 | Multicentre, double-blind, randomised, placebo-controlled, parallel groups | 5 | 148 | 600 | Chronic bronchitis, FEV1 <50% pred, FEV1/FVC <70% pred | NA | 85.6 | 27.1 | NA | 25.4 | 30.0# | 4 |
| Boman et al. [23], 1983 | Multicentre, double-blind, randomised, placebo-controlled, parallel groups | 6 | 203 | 400 | Chronic bronchitis, FEV1 >50% pred | 52 | NA | 81.3 | NA | NA | 80.0# | 1 |
| Babolini et al. [21], 1980 | Multicentre, double-blind, randomised, placebo-controlled, parallel groups | 6 | 495 | 400 | Chronic bronchitis, FEV1 >40% pred | >50 | 76.6 | 66.3 | NA | NA | NA | 1 |
| Grassi and Morandini [28], 1976 | Double-blind, randomised, placebo-controlled | 6 | 69 | 260 | Chronic bronchitis | 61 | 79.7 | NA | NA | NA | NA | 3 |
Data are presented as n, unless otherwise stated. NAC: N-acetylcysteine; ICS: inhaled corticosteroid; FEV1: forced expiratory volume in 1 s; COPD: chronic obstructive pulmonary disease; PFT: pulmonary function testing; GOLD: Global Initiative for Chronic Obstructive Lung Disease; NA: not available; ICD: International Classification of Diseases; ATS: American Thoracic Society; ERS: European Respiratory Society; FVC: forced vital capacity. #: post-bronchodilator not defined.