Becker 2009.

Methods	Open label extension study (3 years findings). No of patients randomised =1280 subjects who previously completed one of the 2 Phase III double‐blind trials (Becker 2005a; Schumacher 2008). No. of patients completing the study = 1086. No. of patients analysed for harms and gout flares = 664
Participants	Inclusion criteria: preliminary criteria of the ACR for gout. Exclusion criteria: pregnancy or lactation; serious drug‐related AE in the prior study; other significant medical conditions that would interfere with treatment harms or compliance; or known intolerance to allopurinol.. Location: 174 centres in the USA and Canada.
Interventions	3 groups: 1. Febuxostat 80 mg/day N = 606 2. Febuxostat 120 mg/day N = 388 3.Allopurinol N = 92 During the first six months of treatment, subjects could switch their febuxostat doses if necessary. Subsequent gout flares treated at the investigators' discretion.
Outcomes	The primary efficacy endpoint: ‐ serum uric acid < 6.0 mg/dL at each visit. Secondary efficacy endpoints: ‐ proportion of subjects with serum uric acid < 6.0 mg/dL at each visit. ‐ percentage reduction from baseline in the serum uric acid concentration at each visit. ‐ incidence of gout flares. ‐ reduction in number of tophi ‐ reduction in the size or disappearance of the index tophus Adverse events.
Notes	Source of funding: TAP Pharmaceutical Products, Inc.
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Low risk	Open label extension from FACT and APEX studies
Allocation concealment (selection bias)	Low risk	Open label extension from FACT and APEX studies
Blinding (performance bias and detection bias) All outcomes	High risk	Open label extension study
Incomplete outcome data (attrition bias) All outcomes	High risk	Efficacy analyses were based on a modified intention‐to‐treat population (only those that received treatment).  There is no description on how incomplete outcome data was analysed
Selective reporting (reporting bias)	Unclear risk	The study protocol is not available, but the authors did not report on 5 of the 9 outcomes recommended by OMERACT(OMERACT 9).
Other bias	Unclear risk	Source of funding: TAP Pharmaceutical Products, Inc.