Dimensionality and measurement invariance of the Serbian version of the BDI-II: An IRT approach

There have been debates about the dimensionality of the Beck’s Depression Inventory - II, its appropriate scoring, and gender-related measurement invariance. We addressed these questions employing the Item Response Theory approach in a clinical sample of 288 patients, using a Serbian version of the BDI-II. We tested nine structural models using confirmatory Full Information Factor Analysis and IRT Graded Response Model. We concluded that the BDI-II is essentially unidimensional. All items had high discrimination, and the test was most informative in the medium range of depression severity in the clinical sample. Although small to medium gender related differential item functioning existed in several items, it did not affect the total score. Hence, the total score of the Serbian translation of the BDI-II is comparable between genders as a measure of severity of depression.