The Utility of the Wisconsin Card Sorting Test in Differential Diagnosis of Cognitive Disorders in Iranian Psychiatric Patients and Healthy Subjects

Article excerpt

Objective: The Wisconsin Test Card Sorting Test (WCST) is a neuropsychological test that has been suggested as a more specific test for frontal lobes dysfunctions. This study was designed to determine whether WCST is able to differentiate between Iranian psychiatric patients with cognitive disorders and normal subjects, and whether WCST scores are related to severity of symptoms in depressive and schizophrenic patients.

Method: Participants were four groups: schizophrenics with positive symptoms (n=25); schizophrenics with negative symptoms (n=25); major depressives (n=25); and normal subjects (n=25). All subjects were tested individually using WCST. To analyze the data, various descriptive statistics, ANOVA, t-test and multiple regression analysis were used.

Results: Regarding the number of categories (P<0.001) and the rate of perseverative errors (P<0.01), according to the results, the normal subjects performed significantly better than patient groups on WCST, although the differences between patient groups were not significant. Our results also showed that greater positive or depressive symptoms were not associated with poorer scores on WCST performance. Only the level of severity of negative symptoms predicted scores on perseverative errors.

Conclusion: It is concluded that WCST can differentiate Iranian psychiatric patients with cognitive disorders from normal subjects, but it is not able to clearly differentiate schizophrenic patients with negative symptoms from those with positive symptoms and depressives. Only severity of negative symptoms affects WCST performance

Keywords: Cognition, Depression, Frontal lobe, Schizophrenia

Iran J Psychiatry 2011; 6: 99-105

Although using neuropsychological tests for differential diagnosis of psychiatric disorders is not new, few studies have been used to investigate the diagnostic strength of such tests in Iran. In recent decades, many researches have used the Wisconsin Card Sorting Test (WCST) to investigate cognitive disorders in different patient groups (1-6). The WCST was developed to assess abstraction ability in normal subjects, but it is now used as a neuropsychological instrument (7-9). The test assesses the ability to form abstract concepts, and shift and maintain the set. Bearing in mind the very high expenses involved in the execution of experiments on psychiatric patients, valid psychological tests can be used as appropriate alternatives to help specialists to achieve differential diagnosis of psychiatric patients. As such the aim of this research is to study the utility of differential diagnosis of WCST in Iranian schizophrenic and major depressive patients and healthy subjects.

WCST has been suggested as a more specific test to forfrontal lobes dysfunctions (10). The frontal lobe patients achieve fewer categories and make more perseverative errors than controls, and they tend to make more perseverative errors than non-perseverative ones (11). Physiological activation of a cortical network was examined during WCST performance in normal subjects. The WCST activation in the dorsolateral prefrontal cortex remained significant even after training and practicing the test (12). It was reported that volume of the dorsolateral prefrontal, as measured by magnetic resonance imaging (MRI), was significantly correlated with the number of perseverative errors in WCST in normal young and old people (13).

Different psychiatric populations show cognitive disorders. Brain-imaging studies have found abnormalities of the structure or dysfunctions of the frontal lobes in many schizophrenic patients (14, 15). Prefrontal gray matter abnormalities in schizophrenic patients may be associated with some symptoms including difficulties with set-shifting and decreased mental flexibility. According to Crow's hypothesis (16), there are two types of schizophrenia: type I and type II schizophrenia. Type I syndrome is characterized by positive symptoms and is presumed to be due to a deficit in dopamine transmission, but type II syndrome is characterized by negative symptoms and is related to structural brain changes. …