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Nav Kapur is a lecturer in psychiatry at the University of Manchester and Manchester Royal Infirmary (Department of Psychiatry and Behavioural Sciences, Rawnsley Building, Manchester Royal Infirmary, Oxford Road, Manchester M13 9WL; tel: 0161 276 5331; fax: 0161 273 2135; e-mail: nav.kapur{at}man.ac.uk). His main research interests include the epidemiology and management of deliberate self-harm and the aetiology of abnormal illness behaviour.
Mistakes are inevitable in any branch of medicine, but psychiatry is a particularly risky business (Holloway, 1997). When psychiatrists get it wrong there may serious consequences for their patients, the clinical team and the wider public. The Government introduced a series of initiatives in the 1990s: the Care Programme Approach (1990), the supervision register (Department of Health & Home Office, 1994) and supervised discharge (Secretary of State for Health, 1997). One of the main purposes of this legislation was to minimise the risk psychiatric patients pose to the community. Future service provision will be shaped by clinical governance and the National Service Framework for Mental Health (Secretary of State for Health, 1997), and evaluation and management of risk will become increasingly important.
Evaluating risk is part of everyday practice. For example, we often need to weigh the risk of harmful behaviour against the benefits of discharging individuals from hospital, or the risk of side-effects against the potential therapeutic benefits of a course of treatment. Holloway (1997) highlights one day's risk decisions in the life of a general psychiatrist. Psychiatric practice could be likened to a minefield. The question is, how do we negotiate it? How do we turn Òan impossible burden" into Òa demanding but intellectually rewarding task"(Holloway, 1998)? In this paper I will discuss the concept of risk and different approaches to evaluating it, as well as considering some of the practical aspects of assessing and managing risk.
| What is risk? |
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Risk tends to be expressed in binary terms, with a person said to be at either high risk or low risk of a particular disorder. This is because most medical decisions and treatments are binary in nature. Our prescribing options for lithium in the prophylaxis of bipolar disorder (to prescribe or not prescribe) depend on our assessment of the patient's risk of relapse (high or low). In fact, classifications of high- and low-risk groups may be largely arbitrary, since most risks are distributed continuously throughout populations (Rose, 1992). However, it has been argued that such dimensional approaches to risk are not clinically useful (Kraemer et al, 1997).
Risk as a dynamic concept
Risk is not static. It varies between populations and across age ranges. For example, marriage is a risk factor for suicide among teenage girls, but a protective factor among adult women (Bancroft et al, 1975; Hawton, 1986). Even for an individual, identified risks can increase or decrease over time, and the nature of the risks may change (Snowden, 1997). This has important implications for risk assessment, which may be no more than a snapshot at one particular moment in time. Risk also varies depending on the stage of the disorder we are considering. The risk factors for a first onset of major depressive disorder are different from those for relapse, which in turn differ from those for remission or recovery.
| Expressing risk |
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| Quantifying risk |
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Actuarial approaches to risk
Statisticians use actuarial to refer to mathematical techniques they apply to set insurance premiums and pension schemes. In the psychiatric risk assessment literature the term has been used to describe any mathematical means of combining information (Buchanan, 1999).
A recent study of suicide in hospital in-patients provides a good example of an actuarial approach to risk (Powell et al, 2000). When 112 in-patient suicides were compared with 112 controls, five factors were found to distinguish particularly strongly between the two groups: recent bereavement, presence of delusions, suicidal ideation, chronic mental illness and a family history of suicide. Ideally, these risk factors would then have been used to predict suicide in an independent sample, but the authors tested the predictive power of the factors in the sample from which they were derived. This is less than ideal, but the results are still of interest (Fig. 1
). Using a cut-off of two or more risk factors to denote high risk of suicide, the specificity of the test (an indication of how well it identifies non-suicides) is very good, at 89/90 or 99%. However, its sensitivity (an indication of how well it identifies suicides) is poor, with only 26/97 or 27% being correctly identified. In other words, we will fail to identify almost 75% of suicides using this test. Of course, we can lower our cut-off so that high-risk individuals are defined as having just one or more risk factors, but this will give an unacceptable number of false positives (non-suicidal patients identified as high risk).
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There are other problems with actuarial techniques (Grubin, 1997). These include a lack of flexibility, poor generalisability across patient groups and limited utility in everyday practice because clinicians often have only fragmentary information on which to base clinical decisions. Actuarial approaches also fail to take into account the individual circumstances of the patient and to provide an explanation of the behaviour.
Newer tools for actuarial assessment have overcome some of these difficulties. One such tool is the iterative classification tree (ICT) for assessing violence risk (Monahan et al, 2000). In a USA study, 106 risk factors in four domains (personal, historical, situational, clinical) were measured at baseline in 939 in-patients. The patients were followed up for 20 months after discharge to investigate which factors were predictive of future violence. The abridged version of the ICT is designed for use in routine practice, and Box 1
shows some of the factors that it considers when predicting risk. The ICT is based on an interactive and contingent model of violence that permits consideration of combinations of risk factors in order to classify a person as high or low risk. The questions are asked according to a tree structure (determined in the original study by statistical consideration of the clustering of risk factors and patients). All subjects are asked a first question. The answer to this determines the next question on the tree and so on until each person is classified into a risk category. One of the advantages over traditional approaches is that this model explicitly acknowledges the fact that violence is an outcome that can be reached by multiple routes. The ICT seems to be superior to existing actuarial risk assessment tools, with only 15% of patients being assigned to an incorrect risk category, but it is still unclear whether the findings are generalisable to the practice of psychiatry in other health care settings.
| Box 1 Factors to consider when assessing violence risk using the iterative classification tree (Monahan et al, 2000) Previous convictions and seriousness of offence Recent violent fantasies Drug use by father Motor impulsiveness Substance misuse Legal status Major psychiatric disorder Diagnosis of schizophrenia Anger reaction Employment status Recent violence Loss of consciousness History of parental fighting
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Clinical approaches to risk
Some view the clinical method of risk assessment as merely an informal and unsystematic version of actuarial approaches and describe clinical experience as Òa prestigious synonym for anecdotal evidence" (Grove & Meehl, 1996). It has been argued that clinicians either allocate patients to reference classes or assign weights to variables and combine these weights mathematically, just as is done using actuarial tables, but that the clinicans do it much less well.
In much of the research literature clinical risk assessment is defined by a process of exclusion and refers to any means of prediction that is not mathematical in nature. It is much more than this. It is a person-specific assessment, which takes into account past behaviour and the context in which it occurred (Vinestock, 1996). It refers to a Òbalanced summary of prediction derived from knowledge of the individual, the present circumstances and what is known of the disorder from which he is suffering" (Department of Health & Home Office, 1994). Central to this approach is a detailed understanding of the person's underlying mental state and psychopathology. The risks in each individual case need to be identified and then assessed in terms of frequency and severity. The assessment process should be multi-disciplinary and information should be obtained from all available sources (Snowden, 1997).
Clinical approaches undoubtedly have drawbacks. When clinicians are asked to predict adverse outcomes they almost invariably overpredict. This is probably because of the relative consequences of the two types of mistake that could be made (Buchanan, 1999). For example, in the current risk-averse climate, most psychiatrists would probably rather detain someone who turns out not to be violent (a false positive) than discharge someone who subsequently commits a violent act (a false negative). This inevitably raises a number of ethical issues regarding the erosion of patients' civil liberties. How many false positives is society prepared to accept in the interests of safety?
Reports from recent inquiries give us a valuable insight into situations where clinical risk assessment has failed to prevent disasters in mental health services (i.e. false negatives). Some of the reasons for failure are listed in Box 2
(Lipsedge, 1995).
| Box 2 Why things go wrong with risk assessment (Lipsedge, 1995) Failure to lend sufficient weight to reports by carers and members of the public about disturbed behaviour Undue emphasis on the civil liberties of patients Failure properly to implement the Mental Health Act Tendency to take a cross-sectional rather than a long-term view of risk Failure to share information in the best interests of the patient
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| Practical risk assessment |
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A risk assessment framework
It may be that the role of risk assessment is not about making an accurate prediction, but about making informed, defensible decisions (Grounds, 1995). The content of risk assessment varies according to the adverse outcome being assessed (e.g. the risk of harm to self or others) and has been comprehensively covered elsewhere (Alberg, et al, 1996; Royal College of Psychiatrists, 1996; Vinestock, 1996).
Moore (1995) suggests a framework that can be applied to most risk assessments in psychiatry (Box 3
). The behaviour to be predicted must be defined and each behaviour should be assessed individually, as each is likely to involve different risk factors. The assessing team needs to distinguish clearly between the probability (likelihood) of the behaviour and its cost (potentially serious consequences). Assessors must be aware of the possible sources of error in the assessment, arising from the patient, the assessors themselves and the context of the assessment. The interaction of internal factors (e.g. attitudes, drives, needs, controls) and external environmental factors (e.g. demands, constraints, stressors) in producing the target behaviour should be considered. A check should be made of whether all necessary information has been gathered. If it has not, what additional information is needed and where might it be obtained? A longitudinal perspective should be adopted, with some prediction of the factors and circumstances likely to increase or decrease future risk. Key interventions should be planned and a decision made about whether to involve other professional groups.
| Box 3 A risk assessment framework (Moore, 1995) Define the behaviour to be predicted Distinguish between the probability and the cost of the behaviour Be aware of the possible sources of error in the assessment Take into account the influence of both internal and external factors on the behaviour Check that all the necessary information has been gathered Predict factors likely to increase or decrease future risk Identify when other professionals or agencies need to be involved Plan key interventions
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Too many decisions, too little time
Sometimes the realities of clinical practice mean that we do not have as much time as we would wish to make clinical decisions. We often have to act in less than ideal circumstances with less than comprehensive information. Three questions might help us to prioritise risk decisions (Taylor 1995): What is the seriousness of the risk? What is the imminence of the risk? What is the probability of the risk becoming actual?
| Managing risk |
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| Risk substitution |
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| Evaluating risks and making decisions |
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Decision analysis involves assigning a probability to each potential clinical outcome. These probabilities represent the doctor's best guess about how likely a particular outcome is, and are based on clinical features and data from relevant clinical studies. A utility is also assigned to each outcome. This represents a patient's preference for one clinical outcome over another. Utilities are given values from 0 to 1 (0=worse possible outcome, e.g. death; 1=best possible outcome, e.g. perfect health). The various decision points and their consequences, along with their associated probabilities and utilities, are mapped to form a decision tree. This is a visual representation of the decisions available. The probabilities and utilities of the various decisions are combined to determine the best treatment. The best treatment is the one with the highest expected utility (i.e. the treatment most likely to provide the optimal outcome for the patient). Figure 2
shows a simplified decision tree for prescribing antipsychotics in first episode schizophrenia with respect to the risk of tardive dyskinesia and recurrence of the disorder. In this example, the expected utility (value) of using antipsychotics or not is calculated by summing the product of probabilities and utility for all outcomes distal to the first branch of the tree. So the expected utility of not using antipsychotics is (0.7 x 0.45) + (0.3 x 1.0)=0.615; that of using antipsychotics is (0.15 x 0.58 x 0) + (0.15 x 0.42 x 0.75) + (0.85 x 0.58 x 0.45) + (0.85 x 0.42 x 1)=0.626. In this case it is better to treat with antipsychotics than not to.
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| Alternatives to a high-risk approach |
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The current management of deliberate self-harm is an example of a high-risk strategy, and it illustrates the disadvantages of this approach (Kapur & House, 1998). First, targeting high-risk groups results in large numbers of supposedly low-risk individuals being defined out of care, reducing the impact of suicide prevention strategies. For example, those identified as being at high risk using one risk assessment scale account for only 26% of cases of future suicidal behaviour, the much larger low-risk group accounting for the remainder. With intervention restricted to the high-risk group, even assuming that it is totally effective (which is improbable), we will reduce the overall rate of suicidal behaviour by at most one-quarter. Second, available risk measures are poor at predicting repeated suicidal behaviour (positive predictive value 25% at best). Third, suicide risk may be continuously distributed in a population, in which case a dichotomous distinction between high- and low-risk groups is not valid.
The population-based strategy of prevention is an alternative to the high-risk approach, and it involves targeting whole populations rather than just vulnerable individuals. This is potentially powerful because of the number of individuals involved; even very small population shifts can have large effects. To use an example from general medicine, a fall of just 3% in the mean population blood pressure reduces the population prevalence of hypertension by 25% (Rose, 1992). Population approaches are also radical since they seek to address underlying causes of a phenomenon rather than just its external manifestations. Again using the example of deliberate self-harm, a population strategy might involve: limiting the availability of methods of self-harm; a review of economic and social policy; and changing our clinical management to offer interventions to everyone following an episode of deliberate self-harm and not just those at high risk.
However, the implementation of population approaches may be unacceptable or prohibitively expensive, and is not always compatible with our medical model of managing health problems. A combination of population and high-risk strategies might be a more feasible and effective option (Kapur & House, 1998). For deliberate self-harm, this could take the form of providing a basic level of intervention for all patients (e.g. an emergency card listing contact numbers) and then using clinical and actuarial methods of risk assessment to identify patients who may benefit from more intensive treatment (e.g. interpersonal or problem-solving therapy).
| Conclusion |
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| Multiple choice questions |
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| References |
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