Development of an abbreviated schizophrenia quality of life scale using a new method

Abstract

The goalof the study was to develop and apply a predictive modelapproach to reduce the number of items collected for scales that yield atotalsummary score. A parsimonious subset of items from the 21-item Quality of Life Scale (QLS) that can accurately predictthe;totalscale score was sought and evaluated in 198 patients with schizophrenia, using a statisticalmodeling approach. Two additionaldata;sets were used for modelvalidation: The subset of 101 patients used in the modelconstruction who had the QLS administered;approximately 1 year later and a new sample of 37 patients. Using only seven QLS items as predictors, the correlation was 0.9831;between the predicted and true QLS totals. Applying the modelbased for these seven QLS items, the correlations from the first and;second validation data sets were 0.9791 and 0.9637, respectively. The study demonstrates that a smallsubset of items of the QLS;predicts the entire 21-item scale with high accuracy. Two validation samples have confirmed the finding. This reduces the effort;associated with scale administration and is likely to increase the assessment of an important functionaldomain. Such models can guide;efforts for item reduction in other rating instruments. © 2003 American College of Neuropsychopharmacology.