When all of the individual items for the final four factors were selected in all sites, we used Confirmatory Factor Analysis in MPLUS to calculate four factor scores in each site separately. The different instruments used have differences in content, objectives, and granularity. For example, the OPCRIT is used to make diagnoses of both psychotic and mood disorders. It contains, therefore, a number of classic manic and depressive symptoms. The PANSS on the other hand, was designed for assessing schizophrenic symptoms and is frequently used in treatment efficacy studies. Its content is therefore geared more towards psychotic agitation and excitement rather than classic manic symptoms. Furthermore, the LDPS comprises 14 more global items, while the OPCRIT has dozens of more fine-grained items and the other instruments are intermediate between these two in granularity.
