Ref (type)	Population	Outcome, Interventions	Results and statistical analysis	Effect size	Favours
Adverse effects
Systematic review	610 people or ears (population not defined) 4 RCTs in this analysis	Tympanosclerosis 1 year 108/305 (35%) with ventilation tube 3/305 (1%) with no ventilation tube	RR 25.9 95% CI 9.0 to 74.9 For details on study quality and heterogeneity, see further information on studies	Large effect size	No ventilation tube
Systematic review	562 people or ears (population not defined) Data from 1 RCT	Tympanic membrane abnormalities 3 to 4 years 185/294 (63%) with ventilation tube 93/268 (35%) with no ventilation tube	RR 1.8 95% CI 1.5 to 2.2 For details on study quality and heterogeneity, see further information on studies	Small effect size	No ventilation tube
Systematic review	218 people or ears (population not defined) 2 RCTs in this analysis	Retraction or atrophy up to 1 year 15/109 (14%) with ventilation tube 10/109 (9%) with no ventilation tube	RR 1.5 95% CI 0.7 to 3.1 For details on study quality and heterogeneity, see further information on studies		Not significant
Systematic review	218 people or ears (population not defined) 2 RCTs in this analysis	Perforation up to 1 year 1/109 (0.9%) with ventilation tube 0/109 (0%) with no ventilation tube	RR 3.0 95% CI 0.1 to 72.1 For details on study quality and heterogeneity, see further information on studies		Not significant
Systematic review	108 people or ears (population not defined) 2 RCTs in this analysis	Otorrhoea up to 1 year 11/54 (20%) with ventilation tube 4/54 (7%) with no ventilation tube	RR 2.8 95% CI 0.9 to 8.1 For details on study quality and heterogeneity, see further information on studies		Not significant