A brief diagnostic screening instrument for mental disturbances in general medical wards

Abstract 

Objective: Mental illness is prevalent among general hospital ward patients but often goes unrecognised. The aim of this study was to validate the SCL-8d as a brief questionnaire for mental disturbances for use in general hospitals. Methods: The study included 2040 patients, 18 years or older, consecutively admitted to 11 general internal medicine wards in seven European countries. All patients were screened on admission by means of the SCL-8d questionnaire. The psychometric performance (i.e., the internal validity) of the SCL-8d scale was tested using modern item response theory (IRT) in the form of the Rasch model. Results: Differences between sample characteristics were considerable. Even so, the SCL-8d scale showed a remarkable, statistically significant fit in terms of internal homogeneity (P>.01) in all individual settings, except in Spain and Germany where the item “Everything is an effort” had to be excluded to obtain a fit. When pooling data from all centres, an excellent statistical significance of fit (P>.05) was obtained by exclusion of the “Effort” item. The scale was homogeneous as to gender (P>.05), but not age as it performed better among young patients than among patients older than 60 years (P<.01). In these two patient groups both internal and external homogeneity (gender, median age) was achieved. The SCL-8d sum score showed a marked correlation with current and previous treatment for mental illness. Conclusion: Apart from the “Effort” item ranking differently on the latent severity dimension as to age, the SCL-8d seems very robust from a psychometric point of view. Besides being short, the SCL-8d scale contains only emotional symptoms. It would therefore seem to be an excellent diagnostic tool for use in medical settings.

Keywords:  Mental disorders, Screening two-phase sampling, Validity, Item response theory, Rasch model, Medical patients, Depression, Anxiety