Test-retest reliability of schizoaffective disorder compared with schizophrenia, bipolar disorder, and unipolar depression--a systematic review and meta-analysis.
OBJECTIVE
Schizoaffective disorder is a frequent diagnosis, and its reliability is subject to ongoing discussion. We compared the diagnostic reliability of schizoaffective disorder with its main differential diagnoses.


METHODS
We systematically searched Medline, Embase, and PsycInfo for all studies on the test-retest reliability of the diagnosis of schizoaffective disorder as compared with schizophrenia, bipolar disorder, and unipolar depression. We used meta-analytic methods to describe and compare Cohen's kappa as well as positive and negative agreement. In addition, multiple pre-specified and post hoc subgroup and sensitivity analyses were carried out.


RESULTS
Out of 4,415 studies screened, 49 studies were included. Test-retest reliability of schizoaffective disorder was consistently lower than that of schizophrenia (in 39 out of 42 studies), bipolar disorder (27/33), and unipolar depression (29/35). The mean difference in kappa between schizoaffective disorder and the other diagnoses was approximately 0.2, and mean Cohen's kappa for schizoaffective disorder was 0.50 (95% confidence interval: 0.40-0.59). While findings were unequivocal and homogeneous for schizoaffective disorder's diagnostic reliability relative to its three main differential diagnoses (dichotomous: smaller versus larger), heterogeneity was substantial for continuous measures, even after subgroup and sensitivity analyses.


CONCLUSIONS
In clinical practice and research, schizoaffective disorder's comparatively low diagnostic reliability should lead to increased efforts to correctly diagnose the disorder.
Department of Psychiatry and Psychotherapy, University of Cologne Medical School, Cologne, NRW, Germany.
Hanno
H
Santelmann
Institute of Medical Statistics, Informatics and Epidemiology, University of Cologne Medical School, Cologne, NRW, Germany.
Jeremy
J
Franklin
Department of Psychiatry and Psychotherapy, University of Cologne Medical School, Cologne, NRW, Germany.
Jana
J
Bußhoff
Department of Psychiatry and Psychotherapy, University of Cologne Medical School, Cologne, NRW, Germany.
Christopher
C
Baethge
D001714:Bipolar Disorder / Q000175:diagnosis / Q000523:psychology; D003865:Major Depressive Disorder / Q000175:diagnosis / Q000523:psychology; D003937:Diagnosis, Differential; D006801:Humans; D011618:Psychotic Disorders / Q000175:diagnosis / Q000523:psychology; D015203:Reproducibility of Results; D012559:Schizophrenia / Q000175:diagnosis*
bipolar disorder; kappa; meta-analysis; nosology; schizoaffective disorder; schizophrenia; systematic review; test-retest reliability; unipolar disorder