Wei 2012.

Study characteristics
Methods	Randomised controlled trial Location of the trial: Harbin, China Method of randomisation: quote: "Randomization was based on a computer‐generated code in blocks of six." Method of allocation concealment: quote: "A copy of the code was stored in a sealed envelope by personnel not involved in the trial." Source of fundings: none
Participants	Inclusion criteria: 2003 Rotterdam ESHRE/ASRM criteria. Oligomenorrhea (interval between menstrual periods ≥ 35 days) or amenorrhoea (absence of vaginal bleeding for at least 6 months) and clinical (a F‐G score ≥ 6) and/or biochemical hyperandrogenism (total testosterone (TT) ≥ 58 ng/dL (2 nmol/L)) were used to assess PCOS. The phenotype of polycystic ovaries was detected by vaginal ultrasound examination presenting 12 follicles or more in one or both ovaries and/or increased ovarian volume (> 10mL) . All participants fulfilled at least two of the three diagnostic criteria. IR was assessed by homeostasis model assessment for IR (HOMA‐IR) ≥ 3.8 or fasting glucose insulin ratio (FGIR) ≤ 4.5 Exclusion criteria: congenital adrenal hyperplasia, Cushing’s syndrome, thyroid dysfunction, hyperprolactinaemia, diabetes mellitus, coronary artery disease, and spontaneous abortion. Furthermore, participants accepting treatment with medications known to alter insulin haemodynamics, ovulation induction, anti‐obesity, or oral contraceptives (OCs) within 3 months were excluded from the study Number of women randomised: 67: MET + OCP arm: 36 OCP arm: 31 Number of women analysed: 58: OCP + MET: 30 OCP: 28 Number of withdrawal and reasons: 9 MET + OCP: 6: 2 loss of F/U: 5.6% 1 personal reason: 2.8% 2 travel difficulties: 5.6% 1 not described in the text (31 in the text/30 in the result table): 2.8% OCP 3: 2 loss of F/U: 6.5% 1 travel difficulties: 3.2% Summary characteristics: PCOS with Insulin resistance Age (years): MET + OCP mean (+SD): 26.03 (2.82) OCP mean (+SD): 26.75 (2.62) BMI (kg/m2): MET + OCP mean (+SD): 24.74 (1.85) OCP mean (+SD): 24.91 (1.66)
Interventions	Treatment: OCP (Ethinyl estradiol 35 mcg Cyproterone acetate 2 mg) cyclically + MET 500 mg twice a day then three times a day Control: OCP (Ethinyl estradiol 35 mcg Cyproterone acetate 2 mg) cyclically + PBO * 2/day Duration: 3 months Co‐intervention(s): diet and exercise
Outcomes	Primary outcomes: Adverse events: severe (requiring stopping of medication) and minor Secondary outcomes: Body weight (kg) BMI (kg/m2) Blood pressure (systolic) (mm Hg) Blood pressure (diastolic) (mm Hg) Serum total testosterone (nmol/L) Free androgen index (FAI) (%) Fasting insulin (mIU/L) Fasting glucose (mmol/L) Fasting total cholesterol (mmol/L) Fasting HDL cholesterol (mmol/L) Fasting LDL cholesterol (mmol/L) Fasting triglycerides (mmol/L)
Subjective outcomes	None
Objective outcomes	(a) clinical parameters: 1. Body weight (kg) and/or BMI (kg/m2) 2. Blood pressure (systolic, diastolic) (mm Hg) 3. Adverse events: severe (requiring stopping of medication) and minor (b) hormonal parameters: 1. Serum total testosterone (nmol/L) 2. Free androgen index (FAI) (%) (c) metabolic parameters: 1. Fasting insulin (mIU/L) 2. Fasting glucose (mmol/L) 3. Fasting total cholesterol (mmol/L) 4. Fasting HDL cholesterol (mmol/L) 5. Fasting LDL cholesterol (mmol/L) 6. Fasting triglycerides (mmol/L)
Notes	Power calculation: unclear
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Low risk	Quote: “Randomization was based on a computer‐generated code in blocks of six”
Allocation concealment (selection bias)	Low risk	Quote: “A copy of the code was stored in a sealed envelope by personnel not involved in the trial”
Blinding of participants and personnel (performance bias) All outcomes	High risk	Quote: “Placebo (provided by pharmaceutical preparation section) was administered as one tablet twice a day.” Whereas MET is given 500 two times/week and then three times/week. Blinding of key study participants and personnel attempted, but likely that blinding could have been broken and the outcome was likely to be influenced by lack of blinding.
Blinding of outcome assessment (detection bias) All outcomes	Unclear risk	Insufficient information available to permit a judgement of ‘low risk’ or ‘high risk’. Blinding not stated.
Incomplete outcome data (attrition bias) All outcomes	Unclear risk	Quote: "Personnal reason, lost of F/U" unclear reason, could be related to intervention. Insufficient reporting of attrition/exclusion to permit a judgement of 'low risk' or 'high risk'.
Selective reporting (reporting bias)	Unclear risk	BP stated in the method not in the result. But not a primary or key outcomes. Insufficient information available to permit a judgment of 'low risk' or 'high risk'.
Other bias	Low risk	The study appears to be free of other sources of bias.