Am J Psychiatry 1995; 152:220-223
Copyright © 1995 by American Psychiatric Association
Spurious precision: procedural validity of diagnostic assessment in psychotic disorders
PD McGorry, C Mihalopoulos, L Henry, J Dakis, HJ Jackson, M Flaum, S Harrigan, D McKenzie, J Kulkarni and R Karoly
Early Psychosis Prevention and Intervention Centre, Royal Park Hospital, Parkville, Victoria, Australia.
OBJECTIVE: Very few studies have quantified the level of agreement among
alternative diagnostic procedures that use a common set of fixed
operational criteria. The authors examined the procedural validity of four
independent methods of assigning DSM-III-R diagnoses of psychotic
disorders. METHOD: The research was conducted as a satellite study to the
DSM-IV Field Trial for Schizophrenia and Related Psychotic Disorders. The
setting was the National Health and Medical Research Council Schizophrenia
Research Unit's Early Psychosis Prevention and Intervention Centre, which
focuses on first-episode psychosis. Consecutively admitted patients (N =
50) were assessed by independent raters who used four different procedures
to determine a DSM-III-R diagnosis. These procedures were 1) the diagnostic
instrument developed for the DSM-IV field trial, 2) the Royal Park
Multidiagnostic Instrument for Psychosis, 3) the Munich Diagnostic
Checklists, and 4) a consensus DSM-III-R diagnosis assigned by a team of
clinician researchers who were expert in the use of diagnostic criteria.
RESULTS: Concordance between pairs of diagnostic procedures was only
moderate. Corresponding levels of percent agreement, however, ranged from
66% to 76%, with converse misclassification rates of 24%-34% (assuming one
procedure to be "correct"). CONCLUSIONS: These findings have significant
research and clinical implications. Despite the introduction of
operationally defined diagnoses, there remained an appreciable level of
differential classification or misclassification arising from variability
in the method of assigning the diagnostic criteria rather than the criteria
themselves. Such misclassification may impede neurobiological research and
have harmful clinical effects on patients with first-episode psychosis.
