Using the Schedules for Clinical Assessment in Neuropsychiatry (SCAN 2.1) as a diagnostic interview providing dimensional measures: Cross-national findings on the psychometric properties of psychopathology scales

BackgroundThe Schedules for Clinical Assessment in Neuropsychiatry (SCAN) is a set of clinical assessment instruments developed under the auspices of WHO. In contrast to other structured diagnostic interviews, SCAN also provides possibilities for dimensional assessment of psychopathology. This paper reports cross-national findings on the psychometric properties of psychopathology scales derived from SCAN 2.1.MethodsWithin a randomized controlled trial, SCAN 2.1 was used in Dresden (Germany), Michalovce (Slovak Republic), Prague (Czech Republic), and Wrocław (Poland). Forty-seven items from Part I of SCAN 2.1, identified as qualifying for constructing dimensional measures, were, on the one hand, grouped according to their allocation to five specific SCAN 2.1 sections. On the other hand, principal component analyses were used to group the items according to their statistical relationship. To estimate the reliability of the scales, Cronbach's α was computed. To assess factor similarity across sites, Tucker's congruence coefficients were calculated. To appraise concurrent validity, mean scale scores were compared across different diagnostic groups.ResultsReliability was qualified as moderate to substantial for all generated scales. Factor-solutions differed across sites. Differences in mean scores supported the assumption that the scales might possess, in addition to face validity, concurrent validity.ConclusionsThis is the first cross-national study on the psychometric properties of psychopathology scales derived from SCAN 2.1, and findings are very encouraging concerning its use as a dimensional measure. However, further studies are needed to substantiate implementation of the scales established.