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A novel multistream triangulation method to define decision thresholds for clinical practice guidelines: a Canadian
Frances Tse1, Nauzer Forbes2, Harminder Singh3
1Department of Medicine and Farncombe Family Digestive Health Research Institute, McMaster University, Hamilton, Ontario L8S 4L8, Canada.
Background And Objectives:
Within the Grading of Recommendations, Assessment, Development, and Evaluation (GRADE) Evidence-to-Decision (EtD) framework, guideline panels must judge the magnitude of health effects (trivial, small, moderate, and large). Current implicit judgments are subjective and susceptible to bias. While GRADE advocates for predefined decision thresholds (DTs), a practical framework to derive them is lacking. We aimed to develop and test a triangulation protocol for establishing a priori DTs for guideline outcomes.
Study Design And Setting:
The methodological framework was developed and applied within a Canadian Association of Gastroenterology guideline on postpolypectomy surveillance, comparing different surveillance intervals, with input from a multidisciplinary expert panel. DTs were derived by integrating 4 evidence streams for prioritized outcomes: (1) benchmarks from prior guidelines, (2) trial-based minimally important differences and model-based large effects, (3) empirically derived generic coefficients, and (4) expert elicitation. A consensus process using a modified Delphi technique (≥80% agreement) established the final DTs.
Results:
A set of DTs (absolute risk differences per 1000 people over 10 years) was generated for outcomes comparing different surveillance intervals. For colorectal cancer (CRC) diagnosis, thresholds for small, moderate, and large effects were 5, 13, and 25 per 1000. For CRC mortality: 2, 5, and 10 per 1000. For major bleeding and perforation, the small effect thresholds were 15 and 7 per 1000, respectively. The process led to excluding "CRC stage at diagnosis" as an outcome but no consensus on advanced adenoma due to debate about its suitability as an outcome.
Conclusion:
This triangulation protocol provides a transparent, operational methodology for setting a priori DTs, addressing a key gap in guideline development and strengthening a critical, value-sensitive step in the GRADE EtD process. Although the process is resource intensive and the thresholds may be context dependent and expert driven, the framework offers a structured, replicable approach that enhances rigor and transparency in one of the most subjective steps of guideline development.
