Alho 2007.

Methods	Allocation: randomised ‐ replacement randomisation Design: parallel groups, average follow‐up about 6 months
Participants	Number: 70 adults out of 298 screened Age: 15 years and above Setting: ENT Department of the University of Oulu Hospital (Finland) Eligibility criteria: 3 or more episodes of pharyngitis in 6 months or 4 episodes in 12 months The signs and symptoms during the episodes had to be typical of streptococcal pharyngitis. In addition, these episodes had to be severe enough for the patient to seek medical attention and at least 1 episode had to be group A streptococcal infection proved by culture or rapid antigen test Exclusion criteria: History of peritonsillar abscess, ongoing antibiotic treatment for other illness, recurrence probably caused by non‐compliance with treatment, major heart or airway disorder or bleeding diatheses that would make same day surgery unfeasible, and residence outside the city of Oulu or the neighbouring 8 communities
Interventions	Intervention group: tonsillectomy (total extracapsular tonsillectomy using blunt or diathermy dissection); n = 36 Comparator group:  watchful waiting (remaining on waiting list); n = 34 Use of additional interventions: participants in the control group did not receive prophylactic treatment for their tonsillitis. No information was provided on any standardised treatment strategy in case of tonsillitis recurrence during follow‐up
Outcomes	Primary outcome: Proportion of patients with an acute episode of group A streptococcal pharyngitis during the 90 days' follow‐up, as determined by signs and symptoms of acute pharyngitis with a positive result of throat culture Secondary outcomes: Percentage change in the proportion of patients with all episodes of pharyngitis at 90 days The times to episodes during the whole follow‐up period The difference in the mean rates of episodes during the whole follow‐up period Days with symptoms (fever, sore throat, rhinitis, cough) during the whole follow‐up period All episodes of pharyngitis (an episode was considered to be at least 2 consecutive days with sore throat) The mean length of follow‐up was 164 (SD 63) in the control group and 170 (SD 12) in the tonsillectomy group Patients recorded episodes and days with symptoms in diaries All participants were advised to visit their own general practitioner if they had acute symptoms suggestive of pharyngitis. The general practitioner would then take a culture sample from the pharynx and send it to Oulu University Hospital for analysis. Patients were given written instructions for their general practitioner about the study and how to obtain the culture sample (from surface of both tonsils or tonsillar fossae in patients who had undergone tonsillectomy and the posterior pharyngeal wall). The patients were told that it was important to seek medical advice for their symptoms during the trial in exactly the same way they had done before the trial and that it was possible to have streptococcal pharyngitis after tonsillectomy
Funding sources	None declared
Declarations of interest	None declared
Notes	Baseline characteristics were balanced
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Low risk	Quotes: "generated the randomisation sequence with a computer random number generator". "To avoid disparity between group sizes, we used replacement randomisation"
Allocation concealment (selection bias)	Low risk	Quotes: "... concealed from the investigators who enrolled the participants ... sequentially numbered sealed opaque envelopes. These were opened sequentially only after an eligible participant had been found and informed consent obtained..." "This task was performed by research assistant not involved in the assignment of care to the trial participants"
Blinding of participants and personnel (performance bias) All outcomes	High risk	No blinding. No information about standardised treatment for sore throats during follow‐up
Blinding of outcome assessment (detection bias) All outcomes	High risk	No blinding. Outcomes were patient‐reported (subjective)
Incomplete outcome data (attrition bias) All outcomes	Low risk	No loss to follow‐up at 90 days. Patients analysed according to group randomised
Selective reporting (reporting bias)	Unclear risk	Insufficient information to permit a judgement of low or high risk
Other bias	Low risk	No other important sources of bias were found Proportion of patients who did not receive assigned treatment: Participants in intervention group who did not have surgery: 0/36 (0%) Participants in control group who had surgical treatment within 90 days: 2/34 (5%), 1 due to pain, another to coincide with another sibling undergoing surgery