Table 3 Key development steps and structural features (left column) relevant to understand and replicate the construction of TPPs. The right column reports possible specific items for the selected step, feature or category. These features are not exclusive, but rather add to those identified by Cocco et al., [13].

1. Defining the purpose and perspective that the TPP will serve

e.g., Regulatory (meet regulatory requirements, e.g. evidence on validation); HTA (define competitive features in terms of cost-effectiveness); other.

2. Choosing the appropriate framework to base the TPP on

e.g., ICH Q8 R2, WHO TPP guidance, FDA TPP guidance, other relevant framework for the specific product to be developed.

3. Deciding on the approach/criteria to choose TPP features and their target levels

e.g., Criteria from previous WHO TPPs, criteria from specific regulations/guidance for the product, etc.

4. Literature review to pool relevant TPP features

e.g., Systematic literature search.

5. Formal consensus approach to agree on most critical TPP features

e.g., Delphi process.

6. Classifying TPP features into categories

e.g., Using common categories appropriate for the field/product (e.g., scope, test performance, operational characteristics for diagnostic tests).

7. Involving relevant stakeholders:

e.g.:

- WHO experts.

- Researchers in the field.

- Manufacturers.

- Regulators.

- End users: clinicians, technicians, laboratory personnel, etc.

- Public and/or Patient population.