Transitivity in the incretin network
Are the trials in the incretin evidence network sufficiently similar to support indirect comparison?
§1Abstract
§1.1Review question
Are the trials in the incretin evidence network sufficiently similar to support indirect comparison?
§1.2PICO frame
Table 1. The registered PICO frame. Any change made after protocol registration is recorded in the amendment log at §5 and is identified there as post hoc.
| Element | As registered |
|---|---|
| Population | Trials contributing to the incretin evidence network. |
| Intervention | Not applicable. |
| Comparator | Not applicable. |
| Outcomes | Distribution of baseline body-mass index, background lifestyle intervention, titration schedule, trial duration and primary analysis timepoint across the network. |
§1.3Method in brief
A review whose unit of analysis is a study characteristic rather than a treatment effect. The protocol was registered with the Institute's secretariat before the search was executed. The search was run on 14 June 2024 across 8 sources and is reproduced in full at §2. Screening, extraction and certainty assessment were performed independently by two members of the secretariat with disagreement resolved by a third.
§1.4Conclusion
Moderate certainty evidence indicates that the transitivity assumption is only partially satisfied. Primary analysis timepoints range from 36 to 104 weeks; background lifestyle intervention ranges from a leaflet to an intensive behavioural programme, and the trial with the most intensive background intervention has a placebo response several times that of the least; and titration schedules differ in a way that affects both efficacy and tolerability. The Institute publishes network estimates with these differences stated at the point of the estimate, and declines to publish a ranking probability, which it regards as a presentation that conceals exactly this uncertainty.
The conclusion rests on 24 contributing studies, listed with their extracted data at §3 and summarised outcome by outcome at §4.
§1.5Limitations
§1.6Consultation
This review was released for public comment before ratification. Draft methodological review: transitivity in the incretin network received 9 submissions. Amendments arising are recorded in the amendment log and are traceable to a numbered submission.