Bayar 2006.

Study characteristics
Methods	Randomised controlled trial Duration and location of the trial: quote: "During the study period of 2004 through 2005, 80 patients with PCOS who attended the outpatient clinics of the Infertility and Reproductive Medicine Unit of the Zonguldak Karaelmas University Hospital (Zonguldak, Turkey) participated in this study.“
Participants	Inclusion criteria: women with anovulatory PCOS diagnosed using 2003 Rotterdam criteria Exclusion criteria: tubal, peritoneal and uterine cause of infertility. Male‐factor infertility. Specific endocrine abnormalities (Cushings disease/syndrome, hypothyroidism, hyperthyroidism, prolactinoma) Number of centres: 1, outpatient clinics of the Infertility and Reproductive Medicine Unit of the Zonguldak Karaelmas University Hospital (Zonguldak, Turkey) Number of women randomised: 80, 40 in group A letrozole and 40 in group B CC Number of women analysed: 38 in group A letrozole and 36 in group B CC Number of withdrawals/exclusions/loss to follow‐up and reasons: 6 lost to follow‐up, no reasons given Age (y): group A letrozole: 32.2 ± 3.9, group B CC: 30.6 ± 4.0 BMI (kg/m²): not stated Duration of infertility (y): group A letrozole: 5 (1‐10), group B CC: 3 (3‐11) Country: Turkey
Interventions	Group A: letrozole, 5 mg/day orally given for 5 days during cycle days 3‐7 Group B: CC, 100 mg/day orally given for 5 days during cycle days 3‐7
Outcomes	Outcomes: ovulation rate by cycle, pregnancy rate by cycle, delivery rate by cycle, miscarriage rate (abortion), multiple pregnancy rate, endometrial thickness on the day of hCG (mm), N of follicles sized > 15 mm in diameter on the day of hCG, E2 level on the day of hCG (pg/mL), E2 per follicle sized > 15 mm in diameter on the day of hCG (pg/mL)
Notes	Ethical approval: yes, the trial was approved by the institutional ethics committee of Karelmal university Informed consent: not stated Source of funding: no funding source or conflicts of interest stated Power calculation: sample‐size determination was based on the difference between the median number of follicles sized > 15 mm and E2 concentration on hCG day. A sample size of 60 participants (30 in each group) was targeted to be able to detect a difference of at least one follicle or of 200 pmol/L between the 2 groups, with alfa (type I error) set at 0.05 and 80% power. We contacted Dr Bayar by email for additional information, but he did not respond.
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Low risk	Simple randomisation performed by a computer
Allocation concealment (selection bias)	Unclear risk	Allocation concealment was achieved by using central consultation for treatment of eligible participants.
Blinding of participants and personnel (performance bias) All outcomes	Unclear risk	Stated as double‐blind but it is not clear who was actually blinded and how this was achieved
Blinding of outcome assessment (detection bias) All outcomes	Unclear risk	Stated as double‐blind but it is not clear who was actually blinded and how this was achieved
Incomplete outcome data (attrition bias) All outcomes	Low risk	6 participants lost to follow‐up, 4 and 2 respectively
Selective reporting (reporting bias)	Low risk	All expected outcomes reported
Other bias	Low risk	None