Reliability and Validity of a German Standardized Diagnostic Interview Module for ICD-11 Adjustment Disorder

The ICD-11 includes a new definition of adjustment disorder (AjD). The present study aimed to examine interrater reliability, internal consistency, and construct validity of a new diagnostic interview module to assess ICD-11 AjD. Data from two studies that used a standardized diagnostic interview assessment (i.e., DIA-X/M-CIDI and updated DIA-X-5) were used. For interrater reliability, agreement indicators (i.e., κ) were calculated using data from the DIA-X-5 test-retest study (N = 60). To examine internal consistency and construct validity, Cronbach's alpha values and the Kuder-Richardson correlation coefficient were computed along with confirmatory factor and latent class analyses (LCA), using data from the Zurich Adjustment Disorder Study (N = 330). Interrater reliability analyses found an adjusted kappa of 0.807 for the ICD-11 AjD diagnosis. Few items from the impairment criterion of the diagnostic algorithm performed poorly. The internal consistency was acceptable, Cronbach's αs = .43-.80; the lower-bound estimate resulted from the two-item preoccupation symptom pattern. However, both items were significantly associated, OR = 3.14, 95% CI [1.97, 4.99]. Regarding LCA results, a two-class model was favored. We found that 94.3% of all ICD-11 AjD cases belonged to Class 2, OR = 23.69, 95% CI [7.15, 79.54], which was associated with subjectively rated distress, OR = 2.18, 95% CI [1.57, 3.02], and the external measure of the Brief Symptom Inventory global severity index, OR = 2.18, 95% CI [1.57, 3.02]. Overall, the new AjD interview module provided a reliable, valid assessment of the ICD-11 diagnosis; confirmation by other studies is needed.