Borgstrom 2017.

Study characteristics
Methods	Double‐blinded, parallel‐group randomised controlled non‐inferiority surgical trial with 1‐year duration of follow‐up
Participants	Setting: Karolinska University Hospital, Stockholm, Sweden Sample size: Number randomised: 79 children Number completed: 74 children Participant (baseline) characteristics: Age: 2 to 6 years Gender: 67% boys, 23% girls Inclusion criteria: age 2 to 6 years, history or symptoms of OSA, tonsil hypertrophy 3 or 4 (scale 1 to 4 according to Brodsky 11), Apnea Hypopnea Index (AHI) of ≥ 5 and ≤ 30 events/hour sleep Exclusion criteria: craniofacial abnormality, neuromuscular disease, chromosomal abnormality, obesity (BMI z score > 1.67), previous adenotonsillar surgery, bleeding disorder, cardiopulmonary disease, history of recurrent tonsillitis and parents with insufficient knowledge of the Swedish language
Interventions	Intervention group: tonsillectomy by cold steel dissection (TE) (n = 40) Comparator group: intracapsular tonsillotomy by coblation (TT) (n = 39) Use of additional interventions: concurrent adenoidectomy in all children
Outcomes	Long‐term outcomes (1 year): postoperative complications, respiratory events during sleep (polysomnography), disease‐specific quality of life, general quality of life, reoperation rates
Notes	Participants lost to follow‐up total: 6%
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Low risk	Quote: "Before study start, 90 sealed envelopes were randomly mixed, 45 for ATE and 45 for ATT, giving a 1:1 allocation ratio"
Allocation concealment (selection bias)	Low risk	Quote: "The envelopes were placed at the operating room and opened by the surgeon"
Blinding of participants and personnel (performance bias) All outcomes	Low risk	Quote: "Only the surgeon and the staff in the operating room knew which surgical method was performed. The surgeon did not meet the patients or parents after surgery; they were discharged by another doctor the day after surgery."
Blinding of outcome assessment (detection bias) All outcomes	Low risk	Quote: "patients and care providers were blinded to intervention method, as was the technologist interpreting the PSGs"
Incomplete outcome data (attrition bias) All outcomes	Unclear risk	6% (5/79) not included in the analysis
Selective reporting (reporting bias)	Low risk	Clinical Trial Registration #NCT01676181
Other bias	Low risk	Baseline characteristics: balanced ITT analysis: performed Formal sample size calculations: performed Use of co‐interventions: balanced, all children received concurrent adenoidectomy