Five-year stability of ICD-10 diagnoses among Chinese patients presented with first-episode psychosis in Hong Kong
Introduction
Diagnosis is regarded as a sine qua non for clinical practice and research (Guze, 1992). Currently, owing to unknown underlying aetiopathophysiology and lack of objective indicator for definitive diagnostic ascertainment, diagnoses of functional psychosis defined by contemporary taxonomies still rely on explicit operational criteria on the basis of phenomenological approach. Although valid diagnoses should be defined by more fundamental characteristics such as physiological, pathological or genetic abnormality (Kendell and Jablensky, 2003), accurate delineation of clinical syndromes can facilitate the process of uncovering biological dysfunctions via enhancing homogeneity (Kendell, 1989, Peralta and Cuseta, 2000). Diagnostic stability is the degree to which a diagnosis remains unchanged at subsequent evaluations (Stanton and Joyce, 1993). It has been suggested as one of the five validating criteria for verifying psychiatric syndromes (Robins and Guze, 1970). It is assumed that the more stable the diagnosis, the more likely it is to reflect a basic and consistent pathophysiological process (Beiser et al., 1989).
In many studies, lifetime diagnosis used for analysis of longitudinal outcome of psychotic disorders such as schizophrenia is based on cross-sectional diagnosis deriving from baseline assessment. Yet, it is known that diagnosis of a given patient can change over time (Chen et al., 1996). Diagnostic change can be attributable to illness evolution and methodological artifacts such as information variance, unreliable assessment, inconsistent application of diagnostic criteria and low inter-rater reliability (Fennig et al., 1994). Diagnostic instability thus raises concerns regarding validity of research results on aetiology, genetics, prognosis and treatment efficacy (Baca-Garcia et al., 2007). Clinically, diagnostic misclassification can lead to iatrogenic effects to patients through inappropriate treatment recommendations (Schimmelmann et al., 2005).
In recent years, a number of studies utilizing first-episode psychosis samples have been conducted to evaluate diagnostic stability over a broad range of functional psychosis (Addington et al., 2006; Amin et al., 1999, Amini et al., 2005, Baldwin et al., 2005, Rahm and Cullberg, 2007, Schimmelmann et al., 2005, Schwartz et al., 2000, Subramaniam et al., 2007, Veen et al., 2004, Whitty et al., 2005). Most of these studies adopted DSM-IV criteria (American Psychiatric Association, 1994) for diagnostic assignment while reports applying ICD-10 scheme (WHO, 1992) were scarce (Amin et al., 1999, Amini et al., 2005) despite the fact that ICD-10 being recognized as the most widely used classification system in psychiatric clinical practice and training worldwide (Mezzich, 2002). Majority of these studies had follow-up duration of less than 2 years (Addington et al., 2006, Amini et al., 2005, Baldwin et al., 2005, Rahm and Cullberg, 2007, Schimmelmann et al., 2005, Schwartz et al., 2000, Subramaniam et al., 2007) and few investigated predictors of diagnostic shifts (Addington et al., 2006, Schimmelmann et al., 2005, Schwartz et al., 2000, Whitty et al., 2005). Besides, almost all first-episode studies investigating diagnostic consistency were conducted in Caucasian populations and only two such studies were done in Asia (Amini et al., 2005, Subramaniam et al., 2007).
Given the clinical and research significance of diagnostic instability, along with its relevance to nosological framework of functional psychosis, we conducted a 5-year retrospective follow-up study to determine diagnostic stability of a representative first-episode psychosis cohort in Hong Kong based on ICD-10 DCR (WHO, 1993), and to assess the pattern of diagnostic change and factors predictive of diagnostic shift towards schizophrenia spectrum disorder.
Section snippets
Subjects
The initial sample comprised 203 Chinese who were consecutively enrolled from July 2001 to December 2002 for initial assessment in a regional first-episode psychosis service in Hong Kong Special Administrative Region (HKSAR) of China. Since 2001 this publicly-funded first-episode psychosis service (abbreviated as “EASY” that stands for “Early Assessment Service for Young People with Psychosis”) has been providing early assessment and intensive case management for all individuals aged 15–25 years
Characteristics of the sample
The 166 subjects were predominantly single (88.6%), 53.6% were male, 94% were living with family and 38.6% were unemployed. Ninety-four subjects of the sample (56.6%) presented as outpatients at entry and the mean age at baseline was 19.8 years (S.D. = 3.11). The mean duration of untreated psychosis (DUP) was 25.1 weeks (S.D. = 30.6, median = 10 weeks), with 56% less than 3 months. One hundred and twenty-six subjects (75.9%) completed 5-year follow-up and the mean follow-up duration of the sample was 53.4
Discussion
Consistent with findings from previous studies, our study showed that schizophrenia and bipolar affective disorder were diagnostically stable with 5-year prospective consistency above 90% (Addington et al., 2006, Schimmelmann et al., 2005, Schwartz et al., 2000, Whitty et al., 2005). The relatively lower retrospective consistency of schizophrenia (82.9%) indicated that there was a diagnostic flux towards schizophrenia across 5-year interval. Schizophrenia was also shown to be a highly specific
Role of funding source
Payment of researchers' salary.
Contributors
Authors WCC and SMC designed the study and wrote the protocol. Author WCC traced medical records, did all data collection and compiled extracted clinical summaries of all subjects. Authors SMC and WSC reviewed the extracted summaries and ascertained research diagnoses for each subject. Authors WCC and LKP performed the statistical analysis. Author WCC wrote the first draft of the manuscript. All authors contributed to and have approved the final manuscript.
Conflict of interest
All other authors declare that they have no conflicts of interest.
Acknowledgements
We thank the staff of the NTE EASY team who provided the data necessary for our analysis.
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