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Study IDs are stored as character values to ensure that zero place holders are not dropped. The randomisation number is assigned sequentially at each site after randomisation. A decimal point is placed between the site code and randomisation number. This allows sites to monitor their own recruitment and ensures the ID can be easily converted to a numerical value if manipulations are required. The study number ensures that samples can that samples and data can be identified across studies. Site codes are based on those that have been used in previously in previous Australasian multicentre trials.
In multiple pregnancy, we recommend one of the following two options to deal with unit of analysis issues:
- Add a suffix where 0 is mother; infants are coded 1, 2 and 3 according to birth order in multiple pregnancy or 5 for singleton. A Note that a surviving twin would be coded as 1.
- Assign a separate "randomisation number" to the fetuses, e.g., start mothers at 1000 and babies at 5000.
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