Refaie 2005.

Methods	RCT Setting: Egypt Method of randomisation: unclear Blinding: unclear Number randomised: 55 total (34 in group 1 randomised to metformin and CC vs CC alone)
Participants	Summary: Group 1 (insulin‐resistant): metformin and CC versus CC alone; Group 2 (non‐insulin‐resistant): CC alone Inclusion criteria: PCOS (Rotterdam criteria) Exclusion criteria: male factor infertility, tubal and peritoneal factors Baseline characteristics of each group: Group 1 (insulin‐resistant) vs group 2 (non‐insulin‐resistant) Mean age (SD) 29 (4) vs 27 (5) Mean BMI (SD) 34.1 (7.9) vs 30.2 (4.6) Mean glucose, mg/dL (SD) 93.2 (11.8) vs 85.1 (12.2) Mean insulin levels, mU/mL (SD) 28.5 (6.8) vs 12.1 (5.4 Dropouts: none
Interventions	Main intervention: metformin 1500 mg/d Duration: 6 months or until pregnancy occurred Co‐interventions: CC 50 mg from day 2 until day 6 of cycle, increased up to 150 mg/d if no evidence of ovulation
Outcomes	Primary: none Secondary: clinical pregnancy rate, ovulation: midluteal progesterone > 10 ng/mL, BMI, fasting insulin, testosterone
Notes	Unable to distinguish baseline characteristics within group 1
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Unclear risk	Inadequate information
Allocation concealment (selection bias)	Unclear risk	Inadequate information
Blinding of participants and personnel (performance bias) All outcomes	Unclear risk	Inadequate information
Blinding of outcome assessment (detection bias) All outcomes	Unclear risk	Inadequate information
Incomplete outcome data (attrition bias) All outcomes	Low risk	No dropouts
Selective reporting (reporting bias)	Low risk	All outcomes were reported
Other bias	Unclear risk	Group 1 was randomised to receive metformin and CC vs CC but there are no baseline characteristics available within these randomised groups