A polydiagnostic scale for dimensional classification of endogenous depression. Derivation and validation.

Several operational diagnoses (OPD) for endogenous depression have been proposed. However--though aiming at similar clinical concepts--the amount of association and agreement between different OPD is rather low. In this study the relationship between eight OPD (Research Diagnostic Criteria, DSM-III, Michigan Discrimination Index, Newcastle Scale I, Newcastle Scale II, Taylor-Abrams Criteria, Vienna Research Criteria, Hamilton Endogenomorphy Index) was assessed by applying latent trait analyses to the classificatory data of these eight OPD which were rated simultaneously in a sample of 173 depressive inpatients. According to these analyses six OPD (RDC, DSM-III, NCS-I, NCS-II, TAC and VRC) are tapping the same phenomenon. This latent trait represents compatible concepts of endogenous depression; it is strongly associated with the independently assessed clinical ICD-9 diagnosis of endogenous depression. The six OPD can be considered as items of a scale (so-called OPD-scale). The total scores of the OPD-scale represent a dimensional assessment of the decisiveness of the diagnosis endogenous depression. Coefficients and parameters of this new scale are presented.