Introduction: The instruments used for the clinical assessment of
schizophrenia and other psychotic disorders are not commonly
administered in routine clinical practice since their application takes a
long time. This study aims to develop a short, comprehensive, and easyto-
apply scale and to examine its psychometric properties.
Methods: A 14-item scale was prepared by adding two items inquiring
about obsessions and memory difficulties to the items taken from
Positive and Negative Syndrome Scale (PANSS) covering the diagnostic
criteria for schizophrenia and schizoaffective disorder. The items were
rated on a 4-point scale reflecting their effect on daily functioning as
1. not present, 2. mild problems, 3. moderate problems, 4. severe
problems. The scale was administered together with other concordant
scales to the patients with schizophrenia and schizoaffective disorder.
The construct validity of the scale was analyzed by explanatory factor
analysis, the concurrent validity was examined through correlations of
the scale scores with those of comparable scales, and criterion validity
was evaluated by the sensitivity to the change in psychopathology. For
reliability, internal consistency coefficient and interrater reliability were
assessed.
Results: Data from a total of 120 patients were analyzed. The internal
consistency coefficient of the scale was calculated as 0.89. Exploratory
factor analysis yielded a 4-factor solution which accounted for 74.47%
of the total variance of the scale scores. The first factor (psychosis)
explained 43.49% of the total variance, the second factor (negative/
cognitive impairment) explained 14.53%, the third factor (emotional
distress) explained 11.19%, and the fourth factor (disorganization)
explained 5.34% of the total variance. Significant correlations were
found between the scale’s total score and the PANSS (r=0.78), Clinical
General Impression-Severity (CGI-S) (r=0.81), and Global Assessment
of Functioning (GAF) scores (r=-0.77). Interrater reliability was strong
(ICC=0.89), and the sensitivity to the change in psychopathology was
significant (Cohen d=2.68).
Conclusion: The scale demonstrated adequate psychometric properties
in terms of reliability, validity, and dimensionality that justify its use in
routine clinical practice.