LAUSR

Abstract Background Current scales of formal thought disorder (FTD) in schizophrenia have been shown to hold considerable inadequacies: 1. The concept of FTD is usually limited to positive and negative symptoms of schizophrenia 2. There is no much consideration about pragmatic disturbances. 3. There are significant inconsistencies in measurements of posFTD and negFTD dimensions (eg, merely focusing on the positive dimension); 4. As to the comprehensive scales of posFTD and negFTD, administration or assessment is time-consuming for routine clinical use and they are not user friendly. Besides, some of the FTD scales include the utilization of materials such as pictures, figures, or extended structured interviews to be able to provide speech samples of the patient. Developing a new FTD assessment tool that can be practically applied in clinic might help clinicans in diagnosis, treatment and follow-up. The aim of our study was to develop a new scale for assessment of FTD and evaluate the reliability and validity of this scale. We named our new FTD scale as Dokuz Eylul Thought Disorder Scale (DETDS). The originality of this scale is based on the fact that it involves assessment of pragmatic comprehension as well as positive and negative FTD and it can be administered and scored practically in routine clinical examination. Methods This study included 130 patients with schizophrenia and 35 controls. For assessing the reliability of this new scale, internal consistency, test-retest and interrater reliability analyses were conducted. The validity of the scale was assessed with concurrent validity and factor analysis methods. Results In the study, Cronbach’s was 0.86. The new scale has a good test-retest (r=0.83) and interrater (ICC=0.985) reliability. The posFTD subscale of the new scale showed high correlation with the posFTD subscale of the Scale for the Assessment of Positive Symptoms (SAPS) (r=0.95, p<0.001) and negFTD subscale of our scale showed high correlation with the alogia subscale of the Scale for the Assessment of Negative Symptoms (SANS) (r=0.95, p<0.001) and impoverishment of thought subscale of the Thought and Language Index (TLI) (r=0.66, p<0.001). The factor analysis revealed a 3-factor solution which explained 74.6% of the variance: 1. Positive Formal Thought Disorder, 2. Negative Formal Thought Disorder, 3. Pragmatic Comprehension Disorder. Discussion Our findings showed that DETDS is a reliable and valid scale which can be used in assessing FTD in patients with schizophrenia in routine clinical use. Unlike most scales of FTD that are available in the literature, but similar to SANS, SAPS, and PANSS, it is practical to use because it is based on clinical interview. Another strength of DETDS is that it intensifies the posFTD and negFTD dimensions and scores them hierarchically in terms of severity. The fact that the new scale covers pragmatic comprehension disorders also presents an innovation to the literature.