Table 2 Considerations in selecting a randomization and allocation strategy
From: Rapid, easy, and cheap randomization: prospective evaluation in a study cohort
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 | |||
- Electronic audit trail created | - Requires familiarity with process | |||
- High cost | ||||
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 | |||
- Audit trail created | - High cost | |||
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 | |||
- Important to ensure treatment assignment cannot be discerned from package features (size, weight) | ||||
- Preparation time/cost | ||||
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 | |||
- Email audit trail created | - Method performance during unsociable hours not yet assessed | |||
- Low cost | ||||
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 | |||
- Audit trail created (allocation paper) | - Participant personal information transferred to allocation paper | |||
- Low cost | ||||
Coin toss | Single site | Low | - Easily accessible | - Only simple randomization (no blocking) |
- Low cost | - No audit trail | |||
- Vulnerable to corruption |