Schizoaffective disorder diagnosed according to different diagnostic criteria - systematic literature search and meta-analysis of key clinical characteristics and heterogeneity

BackgroundSchizoaffective disorder is viewed as a heterogeneous diagnosis among psychotic illnesses. Different diagnostic systems differ in their definition with DSM (-IIIR, -IV, and -V) providing a narrower definition than RDC and ICD-10. It is unclear whether this difference is reflected in patient samples diagnosed according to different diagnostic systems.MethodsExploratory study based on a systematic review of studies of schizoaffective disorder samples diagnosed by either RDC and ICD-10 (group of “broad criteria”) or DSM-IIIR and -IV (“narrow criteria”); comparison (by Mann-Whitney-U-tests) of key characteristics, such as age, number of hospitalizations, or scores in psychometric tests, between more broadly and more narrowly defined schizoaffective disorder samples using standard deviations as a measurement of heterogeneity as well as weighted means and percentages. To reduce selection bias only studies including schizoaffective patient samples together with affective disorder and schizophrenia samples were selected.Results55 studies were included, 14 employing RDC, 4 ICD-10, 20 DSM-IIIR, and 17 DSM-IV. Thirteen characteristics were compared: patients diagnosed according to broader criteria had fewer previous hospitalizations (2.2 vs. 5.4) and were both less often male (42 vs. 51%) and married (21 vs. 40%). Heterogeneity was similar in both groups but slightly higher in RDC and ICD-10 samples than in DSM-IIIR and -IV-samples: +4% regarding demographic and clinical course data and +13% regarding psychometric tests (pooled SD).LimitationsSecular trends and different designs may have confounded the results and limit generalizability. Some comparisons were underpowered.ConclusionsDifferences in diagnostic criteria are reflected in key characteristics of samples. The association of larger heterogeneity with wider diagnostic criteria supports employing standard deviations as a measurement of heterogeneity.