Kamath 2010.

Study characteristics
Methods	Randomised double‐blind placebo‐controlled trial Duration and location of the trial: quote: "This trial was conducted in a university teaching hospital between 2007 and 2009.“
Participants	Inclusion criteria: women with PCOS and clomiphene resistance who were being treated with ovulation induction. Additionally, women had to have a normal hormone profile and a male partner with normal semen parameters by WHO criteria. Normal hormone profile was defined as a FSH level of < 12 IU/L, serum prolactin level of < 25 ng/mL, and a TSH value between 0.3 µIU/mL and 4.5 µIU/mL. Exclusion criteria: women with other endocrine disorders such as Cushing syndrome, and congenital adrenal hyperplasia Number of centres: 1, Reproductive Medicine Unit, Christian Medical College, Vellore, Tamil Nadu, India Number of women randomised: 18 in each group Number of women analysed: 17 in each group Number of withdrawals/exclusions/loss to follow‐up and reasons: 2 lost to follow‐up before treatment started Age (y): group A letrozole: 25.6 ± 3.6, group B placebo: 25.7 ± 3.7 BMI (kg/m²): group A letrozole: 26.1 ± 3.7, group B placebo: 24.7 ± 4.2 Duration of infertility (y): group A letrozole: 5.2 ± 3.2, group B placebo: 3.6 ± 2.2 Country: India
Interventions	Group A: letrozole, orally given 2.5 mg/day for 5 days from cycle days 2‐6 Group B: placebo, also given for 5 days from cycle days 2‐6
Outcomes	Primary Outcome: ovulation rate Secondary Outcomes: live birth rate, OHSS rate, pregnancy rate, miscarriage rate, multiple pregnancy rate, endometrial thickness (mm), day 21 serum progesterone (nmoL/L), number of participants with mature follicle (%)
Notes	Ethical approval: yes, the protocol of the trial was approved by the institutional review board Informed consent: yes, written informed consent was obtained from each participant Source of funding: not stated Conflicts of interest: quote: "The Authors have nothing to disclose" Power calculation: quote: "Our literature pointed to a 75% ovulation rate when 2.5 mg of letrozole was used in women with PCOS who had clomiphene resistance. We hypothesized an ovulation rate of 60& with letrozole and 10% with placebo. On this basis, a sample size of 17 women in each arm (80% and alpha.05 for a two‐sided test) was calculated." Contacted authors about OHSS rate and how randomisation and allocation concealment were done in detail. All information provided
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Low risk	Randomly distributed using a computer‐generated randomisation sequence in blocks of 6, into 2 groups.
Allocation concealment (selection bias)	Low risk	Allocation concealment was done by using consecutively‐numbered sealed opaque envelopes containing the treatment packets.
Blinding of participants and personnel (performance bias) All outcomes	Low risk	The randomisation code was maintained by the pharmacy department, which revealed the group assignments at the end of the trial.
Blinding of outcome assessment (detection bias) All outcomes	Low risk	The code was revealed after the statistical analysis had been performed.
Incomplete outcome data (attrition bias) All outcomes	Low risk	1 woman in each group was lost to follow‐up, after randomisation and before treatment started.
Selective reporting (reporting bias)	Low risk	All outcomes reported
Other bias	Low risk	None