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Department of Psychological Medicine, Imperial College, Charing Cross Campus, London, UK
St Mary's Psychiatric Training Scheme, London, UK
West London Psychiatric Training Scheme, London, UK
St Mary's Psychiatric Training Scheme, London, UK
Department of Psychological Medicine, Imperial College, Charing Cross Campus, London, UK
St Mary's Psychiatric Training Scheme, London, UK
Correspondence: Professor Peter Tyrer, Department of Psychological Medicine, Imperial College, St Dunstan's Road, London W6 8RP, UK. Email: p.tyrer{at}imperial.ac.uk
Declaration of interest P.T. is Editor of the British Journal of Psychiatry, but had no part in the assessment of this manuscript for publication
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ABSTRACT |
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Aims To describe the errors inherent in the current systems and to indicate recent ways of improving personality assessment.
Method Historical review, description of recent developments, including temporal stability, and of studies using document-derived assessment.
Results Studies of interrater agreement and accuracy of diagnosis in complex patients with independently established personality status using document-derived assessment (PAS-DOC) with a four personality cluster classification, showed very good agreement between raters for the flamboyant cluster B group of personalities, generally good agreement for the anxious/dependent cluster C group and inhibited (obsessional) cluster D group, but only fair agreement for the withdrawn cluster A group. Overall diagnostic accuracy was 71%.
Conclusions Personality function or diathesis, a fluctuating state, is a better description than personality disorder. The best form of assessment is one that uses longitudinal repeated measures using a four-dimensional system.
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INTRODUCTION |
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Nevertheless, there have been advances in the assessment of personality disorder and currently a great deal is expected of it in terms of accuracy and precision, particularly in forensic psychiatry. Indeed, a great deal was expected of it in the past, particularly in military psychiatry during the USA in the Second World War, but there it had a poor record of success and had to be abandoned (Wessely, 2005).
Assessment is linked closely to classification and the two subjects need to be discussed in tandem before examining ways of improving current assessment strategies, particularly in the context of new forensic initiatives.
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BRIEF HISTORY OF CLASSIFICATION AND ASSESSMENT |
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When DSMIII was formulated (American Psychiatric Association, 1980) two critical decisions were made. The first was to give personality disorders a separate axis (Axis II) in the classification. The official reason for this was a pragmatic rather than a scientific reason. There was concern, probably justified in view of subsequent developments, that the diagnosis of personality disorder would be forgotten when it competed with other disorders. The unofficial reason was that the psychotherapists advising the task force were very unhappy with much of DSMIII and were offered a separate axis as a quid pro quo for accepting the main Axis I descriptions. ICD10 (World Health Organization, 1992) retained personality disorder on Axis I and introduced Axis II for disability and function, so in this respect, and this only, did it differ fundamentally from DSM. Which is right remains open to much debate, and, after reviewing the arguments Kendell (2002) wrote:
`This separation ensures that consideration is given to the possible presence of disorders that are frequently overlooked when attention is directed to the usually more florid Axis I disorders' (American Psychiatric Association, 1980, p. 23).
`it is impossible to conclude with confidence that personality disorders are, or are not, mental illnesses; there are ambiguities in the definitions and basic information about personality disorders is lacking'.
The second decision was to use clearly defined operational criteria to define the behavioural elements of personality disorder according to the 11 chosen categories in the classification. This was understandable in view of the success of this approach in depression and schizophrenia, but was a mistake with personality disorder. The main reason for the failure of the classification was that the definitions of personality disorder used heterogeneous descriptions, and when all their operational criteria were assessed carefully their distribution was quite unlike that of DSM (Livesley et al, 1994). The alternative of a dimensional classification, most commonly based on traits rather than behaviour, existed before the introduction of DSMIII and has been revised and reformulated many times since (Persly & Walton, 1973; Tyrer & Alexander, 1979; Clark et al, 1996; Mulder & Joyce, 1997; Widiger & Simonsen, 2005), but only now is beginning to have a realistic possibility of being adopted by the world community.
The dimensional system contemplates personality as a continuum, with normal variation at one extreme and what is currently called personality disorder at the other. The best fit is based on four dimensions which are not unlike the original classification system of Hippocrates and Galen (Table 1), particularly when one realises that in the past `sanguine' or `full of blood' was synonymous with confidence and stubborn determination, and `phlegmatic' was equivalent to dull and cold indifference. There continues to be some debate over whether the normal/abnormal personality continuum is best served by three, four or five dimensions (Widiger & Simonsen, 2005), but a very strong case can be made for sticking to four to maintain historical continuity as well as general accuracy (Table 1).
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In examining the assessment of personality disorder it is therefore necessary to examine both dimensional and categorical approaches even though at present both world classifications in psychiatry adopt the categorical model of disorder. However, even if DSMV and ICD11 persisted with the present unsatisfactory system, an alternative one would have to be used to link with studies of normal personality and its variation. As Widiger and Simonsen (2005, p. 126) stated:
`even if the diagnostic manual does not explicitly include normal personality traits, it should be closely coordinated with them so that the APA diagnostic manual of personality disorders is itself well-integrated and coordinated with basic science research on general personality structure'.
The first problem arising in the assessment of personality disorder is the level of agreement between different systems of diagnosis. Others include the stability (or, more accurately, the instability) of current assessment methods in personality disorder, the problem of defining severity, particularly relevant in forensic psychiatry, and the source of information for assessing personality status.
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ASSESSSMENT OF PERSONALITY DISORDER BY CATEGORIES AND DIMENSIONS |
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The best possible level of interrater reliability should therefore come from a structured interview in which assessments are carried out jointly (i.e. the same material is assessed by the two assessors). The disappointing level of agreement shown in such settings is illustrated in Table 2; only one study (carried out with the interview schedule's creator; Zanarini et al, 1987) reached the kappa agreement of 0.75 or above necessary to confirm excellent agreement (Cicchetti & Sparrow, 1981) for clinical purposes.
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However, the level of agreement for the presence or absence of personality disorder is more satisfactory (Table 2), and this tends to be a uniform finding across a range of studies (Bronisch & Mombour, 1994; Zimmerman, 1994, Clark & Harrison, 2001). The mean kappa values for the categorical diagnoses (Table 2) hide tremendous variation as agreement for individual diagnostic categories varies from 0.25 to 0.9. By contrast, when similar assessments are made using the dimensional system the level of agreement tends to show agreement that is consistently 0.10.2 correlation points higher than categorical diagnoses (Loranger et al, 1991; Vittengl et al, 1999). This even applies to individual traits. Thus, for example, in a cross-national reliability study of the Personality Assessment Schedule (PAS; Tyrer et al, 1984) the individual levels of agreement across the separate ratings of 24 traits with both informant and participant interviews (i.e. 48 assessments) ranged from 0.52 to 0.94, with a mean agreement of 0.82 (informant assessment) and 0.75 (participant assessment) (Cicchetti & Tyrer, 1988: p. 71).
If these levels of agreement for categorical diagnosis are the best that can be achieved in ideal research settings with generally cooperative patients using instruments that take between 90 and 360 min to complete, it bodes ill for their reliability in general clinical practice. The problems are made even more profound by the lack of agreement between different instruments. There are now over 60 different interview assessments and self-rated questionnaires for personality disorder and cross-instrument reliability is remarkably poor. Clark et al (1997) found a grand median agreement of 0.27 (kappa) for comparisons of self-report and interview assessments, even though these are allegedly addressing exactly the same personality pathology.
So from these data we have a clear reason why researchers and clinicians are not rushing to assess personality status in their patients, and, when they do, why they use the diagnosis of `personality disorder not otherwise specified' (PDNOS) most frequently (Clark et al, 1995). As two leaders in the field put it, `When researchers use different instruments (interview or self-reports) to identify individuals with personality disorder either in general or with a specific diagnosis they may identify groups of individuals with substantially different characteristics. This virtually guarantees that research results will not replicate, despite the fact that the groups carry the same diagnostic label or both scored highly on scales with similar names' (Clark & Harrison, 2001).
The major reason for the poor agreement is clear, if the operational criteria for individual diagnoses overlap then their identification will lead to the diagnosis of several personality disorders, even when they may be assessing the same single clear construct. The presence of multiple personality disorders is euphemistically called comorbidity, implying the presence of several independent disorders. However, when a diagnostic system fails and splits a common condition into several, the outcome is still called comorbidity when the correct term is consanguinity (Tyrer, 1996). An attempt to redress the confusion created by multiple personality disorders (a term that also cannot be used as it has been appropriated by dissociative disorders in the international classifications) is the cluster model. This has been used in the DSM classification for many years (Reich & Thompson, 1987) and has the advantages of reducing the overlap a little, bringing the odd, eccentric, withdrawn group (paranoid, schizoid and schizotypal; cluster A), the flamboyant, erratic and dissocial group (antisocial, histrionic, borderline and narcissistic; cluster B) and the anxious fearful group (dependent, avoidant and obsessivecompulsive; cluster C), into more natural groupings. However, to fit in well with the four-factor dimensional model (Table 1) there should be a fourth cluster (cluster D) devoted to the obsessional group alone.
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CATEGORIES AND CLUSTERS OF PERSONALITY DISORDER |
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INSTABILITY OF PERSONALITY ASSESSMENT |
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The high level of instability of personality pathology, only a little less than that of major depressive disorder and more so than anxiety (Shea & Yen, 2003), has led to doubts that current instruments, working as they do with a failed classification system, do really indicate that personality is quite so unstable (Wigider, 2005), and there is also evidence of greater stability of social dysfunction in longer-term studies (Nur et al, 2004; Seivewright et al, 2004; Skodol et al, 2005a; Tyrer et al, 2005b). However, the genie is out of the bottle. We can no longer plod forwards developing new instruments that we hope will take us to the Holy Grail of temporal stability (Tyrer, 2005a) and refuse to accept that spontaneous change in personality features can take place independent of any treatment effects.
However, in acknowledging the improvement in clinical samples being treated for disorder we must also note that these populations are relatively uncommon in epidemiological terms. Most individuals with personality disorder (3 out of 4) in contact with services are treatment resisting (Type R) rather than treatment seeking (Type S; Tyrer et al, 2003), and in the normal population this proportion is even higher (C. Kirby, personal communication, 2007). Those with borderline (mainly) and avoidant personality disorders (less prominently) (Emmelkamp et al, 2006) are the ones involved in most of the recent studies, although other approaches, particularly nidotherapy, which changes the environment, not the patient (Tyrer, 2002; Tyrer & Bajaj, 2005), may be suitable for the Type R majority. The findings that one in five children with abnormal personalities get worse in the Children in the Community Study (Cohen et al, 2005) and that older people who have had anxiety and depressive disorders in the past have a higher rates of cluster A personalities than when young (Seivewright et al, 2002) is a reminder that personality pathology can go in different directions. There is also evidence from epidemiological studies that cluster A pathology persists into older age (Reich et al, 1988).
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MEASUREMENT OF SEVERITY OF PERSONALITY DISTURBANCE |
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Unfortunately there is no measure of severity of personality disorder in the ICD or DSM classifications. This absence has caused significant concern, as it is highly relevant to the planning and provision of services. What is clear from empirical research studies is that those with more severe personality disorder do not have stronger manifestations of one single disorder as often postulated (Tyrer & Johnson, 1996), but instead their personality disturbance extends, ripple-like, across all domains of personality, so that in the most severe disorders there is virtually no satisfactory personality function in any area (Oldham et al, 1992; Dolan et al, 1995; Tyrer & Johnson, 1996). By using this measure of severity, and by giving special attention to those with marked antisocial personality features, thereby giving a separate level of `severe personality disorder', it is possible to use the cluster system to get a measure of severity and a reasonable level of agreement (Table 3). This assessment is also relevant in assessing those with the most severe personality disorders, as there is some evidence of a different response in this group in high secure settings (Tyrer et al, 2006).
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PAS-DOC STUDY OF DOCUMENT-DERIVED PERSONALITY ASSESSMENT |
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However, the value of written records describing the patient's attitudes and habitual behaviour has only been appreciated fully by one group, those who measure psychopathy with the Psychopathy Checklist (Hare, 1991). Although the record of inter-rater reliability and predictive reliability of instruments assessing personality disorder is disappointingly poor, the PCLR, and its briefer fellow traveller, the screening version (PCLSV; Hart et al, 1995) go against the trend. These instruments attach great importance to written records without which the full PCLR cannot be completed. The success of the PCLSV in being the best single predictor of violence following the discharge of a psychiatric patient from hospital (Monahan et al, 2001) is unlikely to result from just the presence of superior psychometric properties; the bonus of the additional information derived from records is almost certainly critical, and helps over other methodologies (Moran et al, 2003). This is also important when the data show that half of all people with antisocial personality disorder show no significant violence (Coid et al, 2006b).
We have developed a document-derived version of the PAS (PASDOC) (Tyrer, 2005b) that has the same underlying structure as the parent instrument (Tyrer & Alexander, 1979) but has been adapted for written records, including those about children and adolescents. This latter process has been helped by the modification of the original PAS for use in adolescents where it has been of value (Rangel et al, 2000, 2003). In an extension of the study of patients in the assertive outreach team we assessed both reliability and validity of the PASDOC.
Reliability study
A single typed summary (2 pages) from the case notes of 20 patients
involved in the earlier study with patients in an assertive outreach team
(Table 3) was selected at
random by an independent administrator and given to two assessors (N.C. and
F.I.) who scored them independently using the PASDOC, which gives
personality status after completion of a computer algorithm. The dimensional
ratings of the four main clusters (A=withdrawn cluster, B=flamboyant cluster,
C=dependent cluster, D=inhibited (obsessional) cluster) were rated for
agreement using the intraclass correlation coefficient and also tested for
rater bias (Cicchetti et al,
1976). The results are shown in
Table 5. The best agreement was
reached for the obsessional cluster (RI=0.83), with the
cluster B group (RI=0.74) close behind. The scores for the
withdrawn cluster, A, showed the lowest level of agreement
(RI=0.41).
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Validity study
The 20 patients examined in the reliability study were all very well known
to the clinical team and a consensus agreement of personality status had been
agreed and recorded. A team of five raters, who had received some prior
training only in the original PAS (this included N.C. and F.I. after they had
completed the reliability study and before their data were analysed), each
made an independent assessment of one volume of case notes (which contained
none of the research information on personality status) using the
PASDOC. In assessing the validity of the raters' assessments it was
assumed that a satisfactory assessment would make a correct decision as to
whether personality disorder was present and, if so, in which of the four
clusters it would be placed, or, in the case of more complex personality
disorders, which ones. Diagnostic accuracy was only regarded as positive if
both type and presence or absence of personality disorder were correct.
The results showed that overall diagnostic accuracy was 71%, cluster B personalities were the most accurately identified (88%) and, in contradistinction to the reliability study, cluster D (obsessional/inhibited group) were the least well detected (47%). There was also considerable variation in accuracy between the raters (Table 6). In the context of the results it should be emphasised that all 20 patients had complex pathology (schizophrenia or schizoaffective disorder (11), bipolar disorder (5), recurrent self-harm (1), psychotic depression (1), multiple phobias (1) and obsessivecompulsive disorder (1), with 9 also having a history of drug misuse).
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IMPLICATIONS FOR FUTURE ASSESSSMENT OF PERSONALITY |
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The second conclusion is that a revision of the current classification of personality disorder is overdue. Any changes must take account of the abundant evidence that normal and abnormal personalities merge into each other and it is not appropriate to have one classification for normal variation and another for pathological variation. It is suggested here that four dimensions cover the range of normal and abnormal pathology and that this is the best separation available.
In future, for better assessment we need to have improved global assessments of personality status that can be applied across all age-groups. At present, many investigators, particularly in assessments of children and adolescents, are compelled to pick one aspect of personality functioning at the neglect of others and this may lead to different results between investigators. Thus the study by Viding et al (2007, this issue) describing the significance of callousunemotional traits in the onset of conduct disorder, would be helped greatly by having a much greater breadth of personality assessed, not least because the presence of some more adaptive traits may alter the progression of the maladaptive ones. Similarly, the follow-up of the Aberdeen Children's cohort has had to rely on the Rutter Scale (Rutter, 1967) for recording personality pathology in the flamboyant cluster (Wiles et al, 2005), something that was unlikely to have been anticipated by its originator. In other childhood studies, such as those in which internalising and externalising features are examined (Fergusson et al, 2006), grouping these features by personality status might help to explain much of subsequent pathology (Mervielde et al, 2005; Westen et al, 2005). At the very least this hypothesis should be tested.
With greater awareness of the variability of personality function over time it is also necessary to take more notice of written and other independent evidence about personality status at successive points in time. At present, reliability remains hamstrung by the deficiencies of the current classification, so all attempts to meld and merge diagnoses are bound to fail to some extent because the building blocks are faulty. However, the results with the PASDOC suggest that personality pathology in the flamboyant and antisocial group can, as with the PCLR, be rated both reliably and accurately, but this is more difficult for those aspects of pathology that do not `hit the headlines' as it were, and are confined to more private settings where documentation is poor.
These problems need to be resolved. The work described here suggests that they are being addressed, and this is essential if clinicians are to feel confident about diagnosing clinical problems comprehensively, planning care and predicting outcome for the disorders they commonly treat.
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ACKNOWLEDGMENTS |
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