Table 2.
Considerations in selecting a randomization and allocation strategy
| Method | Best setting | Cost | Advantages | Disadvantages |
|---|---|---|---|---|
| Web-based randomization |
Multisite |
High |
- High reliability 24 h per day |
-Dependent on Internet functionality |
| - Capacity to handle large volume of randomization requests |
- Requires access to a device (usually a computer) to access the Internet |
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| - Electronic audit trail created |
- Requires familiarity with process |
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| |
- High cost |
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| Telephone accessible central coordinating site |
Multisite |
High |
- High reliability 24 h per day |
- Dependent on access to a working telephone |
| - Additional resources associated with a staffed coordinating site |
- Requires staffing of central coordinating site |
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| - Audit trail created |
- High cost |
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| Third party prepared sealed packages of identical appearance |
Single site, multisite possible |
Moderate |
- High reliability 24 h per day |
- Research Assistant or enrolling clinician must know where to find packages consistently |
| - Little time required to obtain participant allocation when implemented optimally |
- Vulnerable to breach of allocation sequence |
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| |
- Important to ensure treatment assignment cannot be discerned from package features (size, weight) |
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| |
- Preparation time/cost |
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| Text message/email method described in this paper |
Single site, multisite not evaluated |
Low |
- High reliability demonstrated in a small cohort |
- Requires both Research Assistant and Randomization Coordinator to have functional smart phone on person with cellular network connectivity |
| - Allocation details received quickly |
- Requires Research Assistant to have functional device that can access study email account via Wi-Fi or cellular network |
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| - Email audit trail created |
- Method performance during unsociable hours not yet assessed |
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| - Low cost |
|
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| Sequentially numbered, opaque sealed envelopes |
Single site |
Low |
- High reliability |
- Research Assistant must be able to access envelopes consistently |
| - Allocation details received quickly |
- Vulnerable to breach of allocation sequence |
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| - Audit trail created (allocation paper) |
- Participant personal information transferred to allocation paper |
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| - Low cost |
|
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| Coin toss |
Single site |
Low |
- Easily accessible |
- Only simple randomization (no blocking) |
| - Low cost |
- No audit trail |
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| - Vulnerable to corruption |