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Probability and loss: two sides of the risk assessment coin

  • Matthew M. Large (a1) and Olav B. Nielssen (a2)

Risk assessment has been widely adopted in mental health settings in the hope of preventing harms such as violence to others and suicide. However, risk assessment in its current form is mainly concerned with the probability of adverse events, and does not address the other component of risk – the extent of the resulting loss. Although assessments of the probability of future harm based on actuarial instruments are generally more accurate than the categorisations made by clinicians, actuarial instruments are of little assistance in clinical decision-making because there is no instrument that can estimate the probability of all the harms associated with mental illness, or estimate the extent of the resulting losses. The inability of instruments to distinguish between the risk of common but less serious harms and comparatively rare catastrophic events is a particular limitation of the value of risk categorisations. We should admit that our ability to assess risk is severely limited, and make clinical decisions in a similar way to those in other areas of medicine – by informed consideration of the potential consequences of treatment and non-treatment.

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Probability and loss: two sides of the risk assessment coin

  • Matthew M. Large (a1) and Olav B. Nielssen (a2)
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Re:Response to Large and Nielssen: Probabilty and Loss

Gordon R.W. Davies, Clinical Associate Professor
19 December 2011

The review of risk assessment by Large and Nielssen(1) is timely as there has been an increasing tendency to rely on structured protocols in the assessment of patients particularly with regard to future probabilities of violence and self harm.However there are a number of important aspects which have not been discussed, the most important of these being the concept of acceptable risk. Although politicians and service managers are happy to point to a process of risk assessment, they universally abrogate their duty as representatives of the community to define what level of risk is acceptable.Despite the statistical difficulties discussed this has been successfully embraced as a concept in aviation medicine. Acceptable failure rates in mechanical components have been used to define the risk management for pilot incapacitation. This approach was pioneered by cardiologists but the principle has been more widely adopted in aviation medicine, even though the definition of base rates of risk in other areas is not as straightforward (2).The acceptance of a defined level of risk has important implications for services. As an example if a patient is considered as being at risk of suicide, rather that the accepted risk being progressively increased as the bed availability declines, the service should have an obligation to provide a bed for those whose risk is considered greater than the acceptable level.Other common areas where risk assessments are required are release of potentially violent individuals from hospital or prison, safety in driving, the ability to own a firearm and suitability for employment in sensitive areas. When these assessments are made it is important that there is not only an understanding of the predictive value of such assessments but that there should be some idea of the relative and absolute risk considered acceptable by the community.Once this is defined then it automatically follows that an adverse result does not imply error. It is important that the community representatives, including coroners and politicians as well as then media, should be educated about this. Ultimately a decision about acceptable risk levels must be explicitly made by the community in advance with regard to their cost benefit ratio. Post hoc assessments of individual decisions are generally unhelpful.In providing reports involving risk assessment I always provide a comment in a report stating that while I have made my own evaluation that I would reconsider my assessment on the basis of a defined acceptable level of risk.Finally I would not agree with Large and Nielssen that risk assessment protocols should not be used. Their importance is not that they produce a usable rating (and I would note that these are strictly ordinal rather than interval scales) but that they do document that appropriate risk factors have been considered in the clinical decisions made.1.Large, M. M. & Nielssen, O.B. Prabability and loss: two sides of the risk assessment coin. The Psychiatrist 2011, 35 (11), 413-4182.Davies GRW, Psychiatry and Fitness for Flying, Practice, Evidence and Principles, Current Psychiatry Reviews, 2010, 6(1), 21-27 ... More

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Response to Large and Nielssen: Probabilty and Loss

Nick J. O'Connor, Clinical Director
07 December 2011

Large and Nielssen's recent article on the predictive value of risk categorisation in schizophrenia is an elegantly written and sobering analysis on clinical risk assessment practices [1]. Their arguments that risk categorisation approaches are limited and may sometimes do more harm than good are reminders of the limitations of the risk management approach. Theimperfect nature of risk categorisation is compellingly demonstrated by application of their HIRC model, applied to the best data available and ina manner that is, if anything, giving risk categorisation the fairest of road tests.Clinical risk assessments, be they based on clinical expertise, structured clinical assessment or actuarial tools are limited because of the mathematics of low frequency events.In probability and loss: two sides of the risk assessment coin[2]. Large and Nielssen advance their concerns about the current practice of risk management by examining the loss element of the risk assessment equation and the current limitation of any instrument to allow for multiplication of the sundry risks that may occur in the course of an unfolding episode of mental illness. They also point out, quite correctly, that clinicians are often operating on limited information. Our own experience with poor handover of all the available clinically important information (from referring clinicians, and family, or medical records stored in another facility) reminds us that even if we had the perfect tool, the risk assessment will only be as good as the information used will allow.These papers will be disconcerting for many clinicians and managers. The changeability of risk and elements of uncertainty in the human interactionof the assessment are other limitations[3]. Added to this is the nature ofthe task of assessing a person whose illness, personality or state of mindmay be constraints to accurate assessment. People may conceal information or their true feelings for a variety of reasons.These arguments against a risk assessment approach to managing clinical risk are important in ensuring against complacency and provide impetus forcontinuing development and refinement of our clinical practice. However, we need also to acknowledge that this is a discussion which is inevitably grounded in a number of frameworks other than the statistical. Large and Nielssen have not made reference to the moral, legal, ethical, cultural, political, compassionate and most importantly pragmatic frames of reference that support continuing to practise a risk assessment approach. While Large and Nielssen's approach is welcome in the arena of scientific discussion, it does not wash in the real world. Winston Churchill famouslyespoused the view that democracy "is the worst form of government except all those others that have been tried". So it is with risk assessment in our current time. The risk management approach when undertaken properly includes participation from a number of stakeholders including the patient, family,and health professionals in efforts to reduce or mitigate risk factors that are drawn from larger population studies, from information available in the clinical encounter and from collateral sources. Assessing risk is atask inherent in psychiatric assessment, and its' importance lies less in the assignation of a category of risk (high, low) than in the way the risks identified inform a treatment or management plan. The plan will ideally include the set of indicated interventions, delivered within an expected timeframe, that are considered best to manage and reduce the risks. There will always be uncertainty whether any risk will eventuate, even for those thought to have a high level of risk. As Large and Nielssenpoint out, this will leave a larger number of people who are judged as lowrisk with no intervention (above standard care), some of whom will turn out to have an adverse event. We are well served if this discussion reminds clinicians, patients and families that we have no perfect powers of prediction and draws the attention of researchers and clinical experts to reach for the next innovation to our methods."The essence of risk management lies in maximising the areas where we havesome control over the outcome while minimising the areas where we have absolutely no control over the outcome and the linkage between effect and cause is hidden from us." (ref)[4]

1.Large M M Ryan C J Singh S P Paton M B Nielssen O B, The predictive value of risk categorisation in schizophrenia. Harvard Review of Psychiatry 2011. 19(1): p. 25-33.2.Large M M Nielssen O B, Probability and Loss: two sides of the risk assessment coin. The Psychiatrist Online 2011. 35: p. 413-18.3.O'Connor N Warby M Rahael B Vassallo T, Changeability, confidence, common sense and corroboration: comprehensive suicide risk assessment. . Australasian Psychiatry, 2004. 12(2): p. 352- 360.4.Bernstein P, Against the Gods: The Remarkable Story of Risk. 1996, New York: John Wiley & Sons.

Dr Nick O'Connor and Assoc. Prof. Scott Clark

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