van Buchem 1981b.

Methods	Randomised ‐ yes, method of randomisation not described Concealment of allocation ‐ adequate Double‐blind ‐ yes Intention‐to‐treat (ITT) ‐ unclear Loss to follow‐up ‐ reasons not described, unclear from which treatment group patients were excluded Design ‐ 2 x 2 factorial design
Participants	N ‐ 202 children (N = 171 children included in analysis; N = 31 were excluded from the study) Age ‐ between 2 and 12 years Setting ‐ both general practice and secondary care: 12 general practitioners in or near Tilburg (the Netherlands) recruited patients and referred them to 1 of the 3 otorhinolaryngologists who excluded those cases where there was disagreement with the diagnosis Inclusion criteria ‐ acute otitis media (AOM) was based on history and clinical picture (i.e. diffuse redness, bulging of the eardrum, or both) Exclusion criteria ‐ antibiotic treatment < 2 weeks prior to randomisation, chronic otitis or otitis media serosa, contraindication for antibiotic treatment Baseline characteristics ‐ balanced
Interventions	Tx ‐ myringotomy and amoxicillin 250 mg 3 times daily for 7 days; N = 48 C ‐ myringotomy and matching placebo for 7 days; N = 36 Use of additional medication ‐ all participants were allowed to use decongestive nose drops and analgesic suppositories (i.e. children aged 2 to 7 years: acetylsalicylic acid 50 mg, phenacetin 50 mg, phenobarbitone 15 mg, codeine phosphate 2.5 mg, caffeine 1.25 mg; children aged 8 to 12 years: acetylsalicylic acid 100 mg, phenacetin 100 mg, phenobarbitone 30 mg, codeine phosphate 5 mg, caffeine 2.5 mg
Outcomes	Main outcomes ‐ (a) parent report of pain at day 0, 1 and 7; (b) otoscopic findings at day 0, 1 and 7; (c) discharge from ear at day 1, 7 and 14; (d) mean temperature at day 0, 1 and 7; (e) AOM relapses at 6 months; (f) audiogram findings after 4 and 8 weeks
Notes	van Buchem 1981b is the 2 arms with myringotomy
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Unclear risk	Method of randomisation not described
Allocation concealment (selection bias)	Low risk	Randomisation performed by otorhinolaryngologists; general practitioner and parent/child were outcome assessors and remained blinded
Other bias	Unclear risk	ITT analysis ‐ unclear, baseline characteristics ‐ balanced
Blinding of participants and personnel (performance bias)	Low risk	Sham myringotomy and placebo was similar with amoxicillin with regard to appearance and taste
Incomplete outcome data (attrition bias)	Unclear risk	Loss to follow‐up/exclusions ‐ N = 31 (15%). Reasons not described

AOM: acute otitis media
 AOM‐SOS: otitis media ‐ severity of symptoms
 C: control
 ITT: intention‐to‐treat
 Tx: treatment