| Methods |
Randomized controlled trial without blinding. The method of randomization and the use of allocation concealment are not described. Communication with the author revealed no extra information. |
| Participants |
489 women at sites in Sweden, Great Britain and Germany. Inclusion criteria were that women had to meet the requirements for the prescription of oral contraceptives in accordance with established medical practice. Limited information about baseline demographics. The paper does not report if switchers were included in the study. |
| Interventions |
Triphasic levonorgestrel/ethinylestradiol (50‐75‐125 μg LNG and 30‐40‐30 μg EE in a 6/5/10 regimen, N=254) [SH B 264 AB] versus
monophasic levonorgestrel/ethinylestradiol (150 μg LNG and 30 μg EE for 21 days, N=235) [Neovletta]. |
| Outcomes |
Principal outcome measures are: pregnancy; side effects; cycle control; discontinuation and reasons for discontinuation. Use of a chart for collecting data on side effects and cycle control. Breakthrough bleeding was defined as intermenstrual bleeding that required the use of sanitary protection and spotting as all other cases including slight brownish discharge. |
| Notes |
The report does not provide an a priori hypothesis or a sample size or power calculation. Study duration: 6 cycles. 36 women in both groups discontinued early. Limited information on number and reasons for discontinuation. The report does not mention the number of women lost to follow up or excluded because of protocol violations. Whether the analysis was based on the intention‐to‐treat principle is unclear. The trial was supported by the manufacturer of the studied monophasic and triphasic levonorgestrel/ethinylestradiol pills (Schering). |
| Risk of bias |
| Bias |
Authors' judgement |
Support for judgement |
| Allocation concealment (selection bias) |
Unclear risk |
No information |
