Psychomotor assessment as a tool to differentiate schizophrenia from other psychotic disorders

The aim of this study is to assess to what extent psychomotor assessment can aid the clinician in differentiating between schizophrenia and other psychotic disorders.

Enrolled subjects were recent in remission patients (n=304), who all met DSM-IV (APA, 2013) criteria for either schizophrenia (Sz; n=117), schizoaffective disorder (SaD; n=36), psychotic disorder not otherwise specified (P-NOS) (n=86), substance/medication-induced psychotic disorder (SIPD; n=33) or major depressive disorder with psychotic features (MDD-p; n=32). The patients were submitted to a psychomotor test battery.

Patients with schizophrenia generally perform worse on most tests. Using cluster analysis a combination of three tests, namely the sensory integration subscale of the Neurological Evaluation Scale (NES), a Figure Copying Task (FCT) and the finger tapping test (FTT), came out to be useful to clinically differentiate between schizophrenia and substance-induced psychotic disorder (SIPD) or psychosis not otherwise specified (P-NOS). When comparing schizophrenia only to a group of patients with SIPD, the differentiation potential becomes even greater with a 76.1% chance to correctly diagnose patients with schizophrenia and 75% chance for patients with SIPD.

A combination of NES, FCT and FTT shows promising results as a clinical tool in daily practice to differentiate schizophrenia from other psychotic disorders. Future prospective studies to confirm these results are necessary.