Third, we attempted to harmonize results across those sites that utilized the same instrument, i.e. the three sites using PANSS and six sites using OPCRIT. For the four selected factors, we compared the EFA loadings in all of these sites on an item-by-item basis. Following convention, we considered an item to load on a given factor if its highest loading was on that factor and was at least 0.4, and if it’s next highest loading was at least 0.2 less than its highest loading. Items which were outliers, i.e. which loaded on a given factor in only one sample without clinical-theoretical justification, and which clearly did not load on that factor in the others, were dropped in all other samples, were included in that factor in all samples. This procedure was followed for the OPCRIT and PANSS sites separately. Factor compositions are described in further detail (28).
