Stafford 1986.

Methods	Allocation: randomised Design: prospective, parallel
Participants	Number: 40 Age: range 16 to 42 years Setting: ENT outpatient department of tertiary centre in London. Patients were referred by general practitioners Male/female: 3/17 in surgery group, 6/14 in antibiotic group Average number of tonsillitis episodes per year: 6 in tonsillectomy, 5 in antibiotics group Eligibility criteria: 16 years or older A history of at least 4 episodes of tonsillitis per year for at least 2 years; each episode consisting of sore throat, dysphagia, pyrexia and general malaise, and lasting a minimum of 3 days Normal full blood count and negative Paul Bunnell test
Interventions	Intervention group: tonsillectomy; n = 20 Comparator group: antibiotics, n = 20 Penicillin V 250 mg, 4 times per day for 8 days for each episode of tonsillitis for the following year Patients with penicillin allergy are given either co‐trimoxazole "2 tablets" 2 times daily or erythromycin 250 mg 4 times per day Use of additional interventions: none described
Outcomes	Time point of measure unclear, most likely between 18 months to 2 years "Cure rate" as reported by patients Patients in the surgery group were reviewed at 6, 12 and 18 months postoperatively Patients in the antibiotics group were reviewed every 3 months in outpatients. GPs were sent questionnaires to complete and return each time a patient was seen and prescribed an antibiotic for tonsillitis
Funding sources	No information provided
Declarations of interest	No information provided
Notes	—
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Unclear risk	Quote: "randomly allocated" No description of allocation concealment method
Allocation concealment (selection bias)	Unclear risk	No description of allocation concealment method
Blinding of participants and personnel (performance bias) All outcomes	High risk	No blinding. Patients, investigators and general practitioners in charge of follow‐up of both groups were aware of treatment allocation
Blinding of outcome assessment (detection bias) All outcomes	High risk	Comment: no blinding. Outcomes were patient‐reported (whether patients "felt cured" of symptoms)
Incomplete outcome data (attrition bias) All outcomes	Low risk	All patients analysed
Selective reporting (reporting bias)	Unclear risk	No access to protocol. Insufficient information to judge
Other bias	High risk	Follow‐up frequency and setting were different between groups. Method of eliciting results most likely different. 6/20 patients in the control arm had received tonsillectomy within 2 years