Item bank measurement of depression: will one dimension work?

Wahl et al. [ 1 ] have provided an elegant exemplar of the psychometric calibration approach known as item banking, applying modern item response theory (IRT) to multi-instrument depression severity measurement. Their inclusive approach, integrative data analysis, and identification of commensurate items from a large number of common scales are enriched by test information functions for each item set, instrument-to-common-metric mapping functions and threshold locations. The authors are to be congratulated on offering a comprehensive standardized view of what might otherwise be 11 unrelated depression metrics. Applied research could unite behind their unidimensional measures.