Adequate allocation concealment | Inadequate allocation concealment |
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Centralized randomization procedures in which the persons including a patient contact the randomization center or a person otherwise not involved in the trial who registers the patient as included in the trial and only then provides the allocation information for this patient | An open random allocation schedule, that is, where all future allocations can be read by an investigator |
Any computerized system that ensures, by password protection or other computer security procedures, conditions 1 and 2 described in the text | Envelopes, if clear details of the procedures used to avoid allocation becoming unconcealed are inadequate, or unclear |
Use of consecutively numbered, opaque sealed envelopes containing the allocation information kept by a person otherwise not involved in the study with envelopes opened only after registration of an included patient | Assignment envelopes were used without appropriate safeguards (for example if envelopes were unsealed or non-opaque or not sequentially numbered) |
 | Alternation, rotation, day of the week |
 | Date of birth, or medical record number |
 | Blocked randomization with block size known to the person including the patient |
 | An unspecified method, for example, if the report states only that "patients were randomized" without giving details of the exact procedures used, and no further information is obtained from the authors. |