CITF Baseline Questionnaire Harmonization Protocol

Metadata schema The repository includes the CITF baseline questionnaire Core Data Element schema, version 3.4. The schema defines 170 target variables and their associated labels, value types, units, permitted categories, missing-value designations, and related metadata. The target variables cover the following areas of information: administrative information; sociodemographic characteristics; lifestyle and behavioural characteristics; physical measures; perception of health and quality of life; health and community-care use; symptoms and signs; laboratory measures; medication and supplements; physical and cognitive functioning; health conditions; and COVID-19 vaccination information reported through the baseline questionnaire.

Dataset structure The harmonized baseline questionnaire dataset is organized at the participant level. Each record represents one participant’s baseline information from the initial questionnaire or chart-review data-collection event. Where relevant information was collected through more than one source instrument, the information is consolidated into a single baseline record.

Records are linked to participants and to the other CITF harmonized datasets using the participant identifier. A separate study identifier is retained to support study identification and data provenance. Harmonization and quality control During harmonization, study-specific questionnaire variables are mapped to the standardized CITF schema.

Variables that directly match a target variable are mapped without transformation. Compatible source variables are transformed to the target format according to documented rules. Variables that were not collected or could not be validly mapped are assigned the applicable harmonization status.

Quality-control procedures include: validation of participant and study identifiers; assessment of record uniqueness at the participant level; standardization of missing values and categorical values; numeric range and non-negativity checks; validation of date values and date components; duplicate-record detection; and assessment of internal consistency. These procedures constitute dataset-level harmonization and quality control.

They do not replace verification against the contributing studies’ original source records. Data access Individual-level baseline questionnaire data are held under controlled access and are not included in this repository. Access to restricted data requires a formal request to the CITF Data Access Office and is subject to applicable institutional approvals, consent conditions, governance requirements, and data-sharing agreements.

Protocol version: 3.5 Metadata schema version: 3.4 Databank release: v1.0