Considerable evidence suggests that the four core criteria displayed in Table 3 should be represented in DSM-5 if it is to possess optimal validity. Therefore, these criteria should definitely be included in any test versions of DSM-5. Any thorough and meaningful development of a TD diagnostic assay should further evaluate the following with regard to criteria and items derived from them (in the case of DSM based questionnaires): (1) cut-scores for multi-category items, (2) cut-scores, weights, or measurement and response option models for scores for the entire set of criteria or items, (3) IRT (item response theory) analyses that evaluate the relation of the criteria or items with the new TD latent variable; (4) measurement invariance analyses that address criteria, item and measure performance across critical populations; (5) need for further criteria and item trimming. It is especially important to determine which criteria or items yield incremental validity when the best performing ones have been entered into prediction models. While some validity data are available on relations of individual DSM criteria with cessation outcomes or smoking heaviness measures [26, 35],
