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

Goal: 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.

Methods: 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.

Results: 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.

Conclusion: 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.