Neurological soft-signs in psychosis:: threshold criteria for discriminating normal controls and for predicting cognitive impairment

It is well established that psychotic patients obtain higher scores on neurological soft-sign (NSS) examinations than normal controls, and also that their cognitive performance is poorer. The aims of the present study were to find threshold criteria that distinguish between normal individuals and patients suffering from psychosis, and to investigate the predictive power of NSS for cognitive impairment. The sample was composed of 56 patients suffering from psychosis and 26 normal controls. Neurological assessment was carried out by means of the Neurological Evaluation Scale (NES), and neuropsychological assessment comprised executive, memory, visuospatial abilities, and attention tests. Receiver operating characteristic analysis was used to assess the diagnostic and predictive efficiency of NSS. A total score of 3 or over on the NES scale, or presence of three or more NSS, proved to be good threshold points for defining 'abnormality' in psychosis patients in comparison with normal controls. NSS presented greater predictive power for cognitive impairment than psychopathological dimensions. Moreover, an NES total score of 8 or higher or, to a lesser extent, the presence of six or more NSS in this scale seemed to be valid cut-off points for predicting severe cognitive impairment in individuals with psychosis. NSS were highly efficient predictors of the presence of severe cognitive impairment related to psychosis. However, their ability to discriminate between individuals with psychosis and normal controls was modest. (C) 2002 Elsevier Science B.V. All rights reserved.