Examples

“This was a multicenter, stratified (6 to 11 years and 12 to 17 years of age), with imbalanced randomization [2:1], double-blind, placebo-controlled, parallel-group study conducted in the United States (41 sites)” [165].

 

“This multicentre, pragmatic, superiority randomised trial compared three parallel groups for patients referred to secondary care for treatment of primary frozen shoulder, who were recruited from 35 hospital sites in the UK. Individual participants were randomly assigned with unequal allocation (2:2:1) to arthroscopic capsular release, manipulation under anaesthesia, or early structured physiotherapy, to allow for different effect sizes between groups” [80].

 

Explanation

The word “design” is often used to refer to all aspects of how a trial is set up, but it also has a narrower interpretation. Many aspects of the broader trial design, including details of randomisation and blinding, are addressed elsewhere in the CONSORT checklist. This item refers to the type of trial (eg, parallel group or crossover) and the conceptual framework (eg, superiority, equivalence, or non-inferiority).

 

CONSORT 2025 focuses mainly on trials with participants individually randomised to one of two parallel groups. While many published trials have such a design, the main alternative designs are multi-arm parallel, [166] crossover, [167] cluster, [168] and factorial designs, [138] with each having their own specific CONSORT extensions. A detailed review of randomised trials published in PubMed in 2012 showed that of the 1122 trials, 953 (85%) were parallel group; the other main designs were crossover (n=98; 13%) and cluster (n=31; 3%). Of these 1122 trials, 892 (80%) had two groups, 146 (13%) had three groups, and 61 (5%) had four or more groups [169]

 

Most trials are designed to identify the superiority of a new intervention, if it exists, but others are designed to assess non-inferiority or equivalence [129]. It is important that researchers clearly describe the design of their trial, including the unit of randomisation (eg, patient, general practice, lesion). These details should also be included in the abstract (item 1b).

 

If a less common design is used, authors should explain their choice, especially as such designs may imply the need for a larger sample size or more complex analysis and interpretation. Although most trials use equal randomisation (eg, 1:1 for two groups), it is also helpful to provide the allocation ratio explicitly.