Protocol and frozen modelling plan: age- and sex-standardised triglyceride–glucose index (TyG_std), version 1.1

This record contains the protocol and frozen modelling plan for TyG_std, an age- and sex-standardised triglyceride-glucose index, together with the R script that implements the modelling procedure and carries the frozen standardisation function. The protocol fixes the form of the standardisation, the seven candidate model families, the pre-specified rule used to select among them, the conditions under which the resulting function is applied to new data, and a summary of the four validation criteria. The model was frozen on 10 October 2026. Version 1.1 (22 October 2026) is a condensed re-issue of that text. One decision rule was amended on 11 October 2026, before the results it governs were interpreted; the amendment, its rationale and its effect are recorded in section 7 of the document. The document contains no results. The companion script runs the frozen transformation and its self-check without any data, reproduces the frozen curve to 1e-8, and terminates if it does not. It requires R 4.3.1 with base R and splines only. This is a secondary analysis of existing observational cohorts with no health-care intervention, so trials-registry registration is not applicable. The frozen model object and the full analysis code are added to this record as a new version once the analyses are finalised; the all-versions DOI resolves to the current version. Licences: this document CC BY 4.0; the R script MIT.