Table 2 Chronic disease outcome metadata schema.

1. General information

 a. Prevalent or incident disease outcome

 I.e., list of chronic disease outcomes examined in the study, differentiating also between prevalent and incident disease outcomes.

 b. Classification system used for the chronic diseases, generally codes of the International Classification of Diseases, Tenth Revision (ICD-10)

 c. Primary or secondary outcome within the study

2. Assessment method: collection method

 a. Self-report

  i. Questionnaire/interview mode and device

  I.e., self-completed: paper-based or computer-based; face-to-face: computer-assisted personal interview (CAPI) or face-to-face paper-based interview; telephone: computer-assisted telephone interview (CATI), paper-based telephone interview.

 ii. Disease domain(s)

  E.g., questions about disease, diagnosis, symptoms, and/or treatment/medication.

 iii. Reference period

  E.g., questions referring to the domain: current, last month, last 6 months, last 12 months, ever.

 iv. Verification of individual cases and/or additional external validation

  E.g., verification methods: hospital/treatment documentation provided by participant, treating physician, hospital/medical records, health insurance, disease registry, death certificate.

  E.g., external validation methods: validation study comparing prevalence/incidence plausibility against a random subsample or a standard, such as medical records of the source population).

 b. Study examinations

  i. Which tests/examinations, including procedures and cut-offs/thresholds

  E.g., blood pressure measurements for hypertension as outcome: three consecutive blood pressure measurements 3 minutes apart. Hypertension if mean systolic blood pressure ≥ 140 mmHg and/or mean diastolic blood pressure ≥ 90 mmHg, and/or use of antihypertensive medication according to ATC code, given the participant had known hypertension.

 c. Administrative databases

  i. Source(s)

  E.g., health insurance, disease registry, death certificate.