[Clinical assessment of schizophrenic syndromes (CASS): rationale, construction, reliability and sensitivity evaluation, and an attempt at normalization of the new diagnostic tool].

UNLABELLED

The CASS (Clinical Assessment of Schizophrenic Syndromes) is a new multi-purpose and multi-level clinical diagnostic instrument consisting of a diagnostic questionnaire (CASS-D) allowing for analysis of a diagnosis of schizophrenia according to DSM-IV and ICD-10 criteria, as well as of three rating scales designed for description and intensity evaluation of schizophrenic syndromes on the global (CASS-G), dimensional (CASS-P, a profile of 13 basic dimensions) or symptomatological (CASS-S, a set of 31 symptoms) level.

AIM

The paper presents a rationale and construction principles of the tool followed by a study of its reliability and sensitivity as well as by preliminary attempt to normalize its results.

SUBJECTS

Twelve trained diagnosticians assessed twice (at the start and end of their hospitalization) 194 inpatients admitted consecutively, within approximately 6 months, to the Department.

METHOD

Results of the CASS were compared with results of the SANS/SAPS, BPRS, and PANSS assessments playing the role of standard, reference instruments.

FINDINGS

High agreement coefficients (kappa) were calculated between a diagnosis of schizophrenia based on unoperationalized (clinical) criteria and operationalized diagnoses based on the CASS diagnostic questionnaire including ICD-10 and DSM-IV diagnostic criteria and algorithms. In the case of both complex (many-item) CASS scales (CASS-P, CASS-S) high reliability measures (internal consistency according to Cronbach's alpha) were found. Characteristics of frequency, intensity and dynamics of the CASS individual symptoms, dimensions and of syndrome as a whole were consistent with expectations based on clinical experience. Direct indices of clinical improvement calculated from CASS-G, CASS-P or CASS-S scores obtained at two time-points (admission, discharge) correlated fairly highly with more direct measures based on diagnosticians' clinical global impressions made when summing the results of treatment at discharge from the hospital. This finding suggests that CASS scores may sensitively register changes in patients' mental state during hospital stay and treatment. On the base of empirical distributions of CASS scales, a normalization (sten-scales) was proposed which may be useful for comparison of results obtained in differing groups of patients. Analysis of percentile and sten distributions of the CASS-P and CASS-S pointed out that patients with a diagnosis of schizophrenia had higher mean scores than patients with other diagnoses. This observation as well as above mentioned reasonableness (consistency with clinical experience) of a picture and dynamics of schizophrenic syndromes revealed in CASS assessments may be treated as preliminary assumptions of its content validity.

CONCLUSIONS

Results of the study suggest that CASS has satisfactory measures of reliability and sensitiveness. They allow for a preliminary normalization of its scales and prompt to study its validity.