Parallel Assignment Study

A Parallel Assignment Study is a Interventional Clinical Study in which patients' assignment and treatment administration are conducted simultaneously so that experimental and control groups are in parallel.

• AKA: Parallel Design, Parallel Group Clinical Trial.
• Context:
  • It often consists of assigning clinical trial participants to both treatment and control groups over the same period of time.
  • It is often used to compare clinical efficacy and safety among the treatment groups.
  • It typically assigns each person randomly to one treatment group.
  • It often adopts randomization to remove treatment selection bias and promote comparability of treatment groups.
  • It can range from being a Two-Arm Parallel Clinical Trial to be an N-Arm Parallel Clinical Trial.
• Example(s):
  • National Emphysema Treatment Trial (NETT),
  • …
• Counter-Example(s):
  • Adaptive Clinical Trial,
  • Crossover Clinical Trial,
  • Factorial Clinical Trial,
  • Large-Simple Clinical Trial.
• See: Group Allocation, Randomization Unit, Clinical Trial Arm, Placebo-Controlled Clinical Trial, Equivalency Clinical Trial, Superiority Clinical Trial, Non-Inferiority Clinical Trial.

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References

2022a

• (ClinicalTrials.gov, 2021) ⇒ https://clinicaltrials.gov/ct2/about-studies/glossary Retrieved 2022-01-15.
  • QUOTE: Parallel assignment: A type of intervention model describing a clinical trial in which two or more groups of participants receive different interventions. For example, a two-arm parallel assignment involves two groups of participants. One group receives drug A, and the other group receives drug B. So during the trial, participants in one group receive drug A "in parallel" to participants in the other group, who receive drug B.

2022b

• (Coursera, 2021) ⇒ "Design and Interpretation of Clinical Trials" (adaptation).
  • QUOTE: In a parallel design, we are assigning patients and administering treatment, so that the experimental and control groups are in parallel. In other words, we are assigning people to both groups, over the same period of time, as opposed to collecting data on the experimental groups only, and comparing that data to historical controls, or as opposed to assigning treatment A and then assigning treatment B in series.

    Each person in a parallel design is assigned to only one treatment group. The process by which we allocate people to a specific treatment group is usually a randomization process. We use randomization to allocate patients because it removes bias in the allocation process, which is called selection bias.

Figure 1: Parallel Design Graph.

• 1. We start with the defined population or the group of people who are eligible for our trial.
• 2. Then through an allocation process, usually randomization, we decide who is assigned to which treatment group. As shown in picture above, we are deciding who will be assigned to receive the new treatment versus who will be assigned to receive the current treatment.
• 3. In the bottom row of boxes, we see that we will observe after some period of time, who among those assigned to new treatment has improved and who has not improved, and who among those assigned to current treatment has improved and who has not improved.

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