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University Hospital of Wales, Heath Park, Cardiff CF14 4XW, UK
Correspondence: S F S Halpin, University Hospital of Wales, Heath Park, Cardiff CF14 4XW, UK. E-mail: halpinsf{at}cardiff.ac.uk
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Data from the National Audit Office in 2005 [7] found the following:
The great majority of errors do not result in a legal action for negligence — Harpwood estimates a rate of 7% [7] — but the annual cost to the NHS in 2004/5 of clinical negligence claims was £502.9 million [7].
Errors in radiology
Reason's [8] book on error has become the standard text. He considers an error to have occurred when a desired outcome is not achieved, excluding the intervention of chance. Merry and McCall Smith [9] consider that the definition of error must focus on intention rather than outcome, because some errors do not alter outcome unfavourably and near-misses, for example, deserve attention. Their book, "Errors, medicine, and the law" [9], is highly recommended reading for all doctors. Green [10] divides errors between three main groups: errors of perception, errors of intention and errors of execution. Errors of perception account for the majority of radiological errors. A perceptual error is in fact a complex mix of three different factors. A radiologist must have sufficient knowledge to be able to search for an anomaly; having perceived it, he or she must make a judgement as to whether it is a normal variant, a pathological lesion or an artefact. An error in any of these elements may lead to a wrong report. Knowledge, perception and judgement are three different cognitive skills, all of which are subject to failure. The causes of such failure have been investigated extensively [11–18], but they remain part of the human condition and can never be eliminated. Psychological processes such as "satisfaction of search" [19], "search for meaning" [20] and the "cocktail party effect" [21] explain both the logical leaps that can lead to a diagnosis and why perceptual errors are intrinsic to these processes.
All radiologists are aware of the frailties of perception and do their best to avoid perceptual errors but, unfortunately, an over-eager search of an examination can lead to false-positive diagnoses [22]; e.g. at least 10% of lesions reported as cancerous on mammography turn out to be benign [23]. Apart from the obvious morbidity that may accompany false-positive diagnoses, NHSLA data show that radiologists are also sued for these errors. It is, after all, very hard to explain to a judge why a specialist radiologist failed to notice an abnormality that is obvious, even to the judge. The fact that all radiologists sometimes miss "obvious" lesions is accepted in the radiological community. Such errors are at the heart of the complex cognitive processes of perception.
The process can be likened to a "spot the difference" puzzle. Two people doing the same puzzle will find the differences in a different order to each other. A difference hidden to one observer will be readily apparent to the other, and vice versa. But once the answers are revealed, neither observer will be able to explain why they could not find the "obvious lesion". And every time the puzzle is reviewed, the previously obscure differences will stand out as readily apparent.
Berlin [17, 24–27] has written extensively in the American literature regarding errors in radiological interpretation but, as he points out, the error rate has not changed significantly over the last 50 years since Garland wrote on the accuracy of diagnostic procedures in 1959 [28]. A second viewing of the same film by the same radiologist will result in a different report in as many as 20% of occasions [12], and Goddard et al [29] reported discrepancy rates of as high as 20% between reports, where the alternative reports would cause clinically significant changes in the patients management. Berlin [27] states that, where a study reveals an abnormality, discrepancy rates between radiologists average 30%. If all films are taken into account (bearing in mind that most will be normal), the discrepancy rate is
4%.
Berlin [27] aptly quotes Robinson [30]: "although technology has made enormous progress in the last century, there is no evidence for similar improvement in the performance of the human eye and brain".
Can all of these errors be negligence?
Recent changes in the law
Clinical negligence occurs when a patient comes to harm as a direct result of a doctor failing in his or her duty of care [4]. In order for a claim for negligence to succeed in the courts, each of these components has to be in place. As a doctor's duty of care to the patient is seldom questioned, negligence cases usually turn on whether the doctor failed in his duty, and on issues of causation.
Perhaps surprisingly, very few medical negligence cases succeed in court. According to the Royal Commission on Civil Liability and Compensation for Personal Injury [31], only 35% of claims are successful, compared with a rate of 60–80% for other negligence claims reaching court. This has been the subject of much academic debate among the legal profession [32] and, for many years, lawyers have been seeking to redress the balance (as they see it) to enable more patients to recover damages from doctors after an adverse event.
As recently as 2001, Lord Woolf [33] wrote that he considered that the courts had been too deferential to the medical profession, and that this balance was changing.
Why do most clinical negligence cases fail? Most often, it is the issue of causation. The law has always required a direct and absolute connection between the failure of duty and the harm caused. In the medical setting, it is often difficult to separate out other natural causes of harm. A surgeon was found not guilty of manslaughter when a patient died after removing their healthy kidney instead of the diseased one because the final cause of death was pneumonia, not renal failure; the causal link between the wrongly performed operation and death was not strong enough. However, recent changes in case law have combined to weaken the defendant doctor's position.
In Bolitho vs City and Hackney Health Authority [34], the House of Lords seriously damaged the Bolam defence whereby a doctor could not be found guilty of negligence if he could show that a body of medical opinion agreed with his or her management. Although a detailed discussion of this case is outside the scope of this article, the Law Lords decided with a majority verdict that, in order for a medical opinion to valid, it must be "reasonable, responsible, and respectable", and be able to withstand logical interrogation. In other words, judges can, in some circumstances, dismiss a Bolam defence if they consider it illogical. It is no longer sufficient for a defendant to show that other doctors agree with him: these doctors must now defend their position. For example, it may not be possible to justify an opinion that conflicts with National Institute for Clinical Excellence (NICE) guidelines [35].
In the context of a claim against a radiologist, it may be difficult for a colleague to defend a radiologist who, in a perceptual error, has missed a cancer. Will the judge find that to miss a lesion, so often obvious in retrospect, even to the judge, is compatible with logic?
Chester vs Afshar [36] concerned a patient who suffered a permanent paraparesis after a lumbar spine operation. It was accepted by the courts that the operation was carried out skillfully, and that paraparesis was an accepted risk of the procedure. However, the courts found that the surgeon had failed in his duty of care in failing to properly warn the patient of this risk. It is only fair to say that the surgeon disputed this finding, but the issue of consent was not further discussed by the time the case came to the House of Lords. In the past, the issue of causation in this situation would mean that the claimant would have to prove that he or she would not have undergone the surgery if warned of the risk, but the patient in this case said that she would have had the (highly necessary) operation, but would have delayed it until a later date. In finding for the claimant, Lord Steyn broke the previously impregnable link between incident and causation. He said "I am glad to have arrived at the conclusion that the claimant is entitled in law to succeed. This result is in accord with one of the most basic aspirations of the law, namely to right wrongs. Moreover, the decision announced by the House today reflects the reasonable expectations of the public in contemporary society".
In other words, his decision was influenced by public expectation and was, in the authors opinion, a policy decision to move forward the law of negligence. He quoted with approval the commentary by Professor Paul Honore on a similar Australian case [37]. Honore specifically endorsed the use of policy and corrective justice to make a defendant strictly liable, to make sure that justice is done, and to vindicate a plaintiff's rights, even in the absence of causation. The term "strict liability" has not previously been used in UK clinical negligence cases, and in a legal sense it means that, after an accusation of negligence, the burden of proof falls upon the defendant to prove that there was no negligence, rather than on the claimant to prove that there was. Reversing the burden of proof in medical negligence cases has long been an aim of pro-patient charities like Action against Medical Accidents (AvMA), but such a departure would bring a sea-change to the world of medical negligence.
How does this ruling affect a radiologist? Take for example a patient who suffers harm after a missed diagnosis of breast cancer. The patient may have been seen by two or three doctors who did not find a breast lump. Microcalcification on a mammogram might have been interpreted as benign, or just missed. But when the patient returns 6 months later with advanced cancer and a large palpable lump, it is only the radiological examination that is available for re-evaluation. If a clinician failed to notice a small lump, his or her judgement can never be questioned. But the radiologist's judgement is permanently recorded and ready for retrospective analysis. In the knowledge of the outcome, it is very easy for any number of experts to demonstrate an abnormality to the judge, and explain that such an appearance must be considered as evidence of malignancy. Having been shown the differences between two pictures, it is easy to demonstrate them to a third party.
Faced with the patient who has suffered and an "obvious" lesion on the mammogram, can a judge be made to understand the vagaries of radiological interpretation? Outcome and hindsight bias are two factors that work against the defendant radiologist. These are psychological factors inherent in us all, making us judge more harshly an incident once we know of a bad outcome and the eventual confirmed diagnosis. Hindsight is a powerful psychological tool, and Fischoff and others [38, 39] have demonstrated that knowledge of the outcome of an event influences how it is assessed in retrospect [26, 40, 41].
Following Lord Steyn in Chester vs Afshar [36], does it not fit a policy of corrective justice and the expectation of society to find the radiologist guilty of negligence and compensate the patient — to right the wrong? Although root cause analysis of adverse events often shows that an incident is either due to system failure or a culmination of small events [42], it is often the radiologist who is left holding the smoking gun.
Error or negligence?
Is it possible for a doctor to make an "honest mistake", or is every slip or lapse made by a doctor to be interpreted as a failure in a duty of care? Is there evidence in English law that doctors who make perceptual errors are punished for the sort of mistake that every radiologist makes every week?
From the NHSLA data presented above, it is clear that some areas of radiology are particularly at risk. In Cardiff, mammography represents 1.4% of radiological work (Cardiff and Vale NHS Trust and Breast Test Wales, personal communication), but the NHSLA data show that 16% of claims against radiologists involve breast radiology. In contrast, musculoskeletal radiology accounts for 28% of claims, but this is roughly appropriate to the number of musculoskeletal examinations performed. Breast cancer is approximately as common as lung cancer, but far fewer claims have been made after delayed diagnosis of bronchial carcinoma.
There are only two possible explanations for this disparity: either breast radiologists are careless doctors who are more likely to practice negligently than others, or breast radiologists work in a field that is subject to a particularly difficult perceptual task. It is submitted that the latter explanation is much more likely.
It does not fit natural justice that one group of doctors should be held more accountable to the law than others practising in the same department, doing similar work, with a similar degree of care. But how can a doctor accused of negligence after missing a cancer demonstrated in retrospect defend himself in court?
Possible solutions
The issue needs to be addressed from more than one angle. Firstly, radiologists themselves need to be aware of the cognitive and psychological processes inherent in the perceptual tasks of radiology reporting. In the author's experience, these processes are poorly taught in training programmes but, to a limited extent, forewarned is forearmed.
It is then necessary to educate our colleagues, the judiciary and the general public in the difficulties of radiological interpretation, and even to publish the number of mistakes made every day in Radiology departments. A major factor in a claim being brought is that, once a cancer is missed and the patient tries to find out what went wrong, the perceptual error will often be obvious even to the lay person, who cannot understand how an expert could miss such an obvious thing. The error is prima facie evidence of negligence.
However, the law could not, should not and will not allow radiologists a blanket defence of "common perceptual error", which might allow a careless doctor to practise recklessly. If we are to convince others that we do not act negligently, then we must supply evidence of careful and safe practice, and publish the evidence for our peers and our patients to read.
Quality control
There is some evidence in law that robust quality control mechanisms can protect against allegations of negligence, albeit from consumer protection law, where strict liability is the norm [43]. It is proposed that radiologists should build a revalidation portfolio based on a consistent, coherent and regular peer review of his or her reports. This would accrue over time to be a database of hundreds, and eventually thousands, of cases that have been verified. A small number of reviewed cases each week would quickly build into a significant bank of evidence, demonstrating that the doctor maintains his knowledge and skills. The reviewer would have to have the same area and level of specialisation and, when the doctor works in a particularly unusual speciality, periodic external peer review might be required. Of course, many radiologists already do this, but by no means do all formalise peer review.
In breast screening, national audit programmes are in place, and national audits are the norm in pathology. An element of external peer review would avoid allegations of collaboration between colleagues. The specialist groups within the Royal College of Radiologists could play a role in distributing anonymised test cases on digital media or through a web-based system, which would provide an element of external review for all.
The recent report published by the Chief Medical Officer [44] indicates that all doctors practising in England will have to reapply for a licence to practise every 5 years, and that the application must be supported by evidence from audit and clinical governance. Peer review of radiology reports will soon become mandatory. Radiologists should embrace it, ensure that their job plans contain time for peer review, which need not be an adversarial process, and use the data as evidence of safe practice.
It is the nature of statistics that 49% of radiologists will be below average on each test, and this would have to be taken into account, most simply by incorporating several "rounds" of review before releasing results into the public domain. The great majority of radiologists will be at (or close to) the average, but inevitably some radiologists will be shown to be performing poorly in one or more areas. This needs to be identified for the public good, and such doctors should undergo retraining or redeployment into other areas. It is also likely that some areas of radiology will be shown to have a relatively low error rate, and others a higher one. Perhaps mammography will be one of the latter. In this case, Trusts will need to consider whether all of these examinations should be double-reported in order to reduce error. Perhaps patients should insist on it.
Public information
Doctors have been accused of cultivating a reputation for infallibility [45], and it is submitted that the view of a doctor as someone who does not make mistakes is unhelpful to both patients and the profession. On the one hand, patients need to be able to trust their doctor, and believe that the doctor will help to cure them but, on the other hand, if a patient has a mammogram which is incorrectly reported as normal, then she might be reassured falsely and may ignore symptoms of early cancer. All the psychological evidence states that doctors make errors, and it seems that radiologists are particularly prone to errors of perception: this fact should be made public. There is growing evidence in the USA of a general and judicial awareness of the inevitability of human error [20, 46, 47].
One of the reasons why claims against radiologists are made is the public perception that a specialist radiologist should see and report all abnormalities on radiological images, particularly when these are "obvious" and can be seen in retrospect by even a lay observer.
Surgeons and other doctors who perform practical procedures, such as cardiologists or interventional radiologists, will never carry out a procedure without discussing the risks of the procedure, and the likelihood of success or failure, with the patient. This establishes a personal relationship between clinician and patient, and limits expectations. The signed consent form has weight in law if it is agreed that, in signing the form, the patient has understood the nature and purpose of the procedure, together with its attendant risks and benefits. In diagnostic radiological examinations, however, consent is implicit. There is no direct doctor–patient relationship, and no understanding by the patient of the complexities of radiological diagnosis.
It is clearly impractical for a radiologist to meet every patient who comes for a radiograph. However, it would be possible to manage patients expectations by a carefully worded information leaflet which, in the case of mammography, would intimate the difficult nature of mammography reporting and emphasise the need for a patient to discuss the result of her test in the light of her symptoms and signs. It would be entirely feasible to publicly display the audit results of the reporting radiologists either in the department or within the leaflet. This might take the form of:
"The radiologists who will report your mammogram are Dr Smith and Dr Jones. Together, they have 14 years of experience in diagnostic mammography, and they will take all appropriate care in looking at your films. Both Dr Smith and Dr Jones undergo regular training and assessment to maintain and test their skills, and internal and external peer review of their work has shown that their accuracy in reporting mammograms is very similar to that of other doctors in their field. However, no human being is perfect, and some abnormalities could be overlooked, and so if you develop, or are worried by, any symptoms, then it is important that you discuss these with your doctor, who can ask us to review your films whenever appropriate."
Many doctors would find such directness initially difficult and disturbing, and inevitably predictions would be made that such openness would surely lead to more claims and not fewer. However, limited evidence from Kentucky suggests otherwise [48]. The initial public response might also be unfavourable. Some patients would not want to hear of their doctors' mistakes, and there would be a risk that some would not attend screening examinations owing to a loss of confidence in the accuracy of the system. It is submitted though that informing the public and limiting unrealistic expectations would go a long way to reducing claims caused by a lack of understanding of the nature of radiology, and this view has some support in the USA [25]. Lord Steyn's dictum in Chester vs Afshar indicated that a judgement against the surgeon was in keeping with public expectation. To modify public expectation, therefore, should provide some protection in a clinical negligence claim.
| No-fault compensation? |
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Caldwell and Seamone [20] have proposed in the USA that a legal defence of "excusable neglect" exists, and that this should apply to radiological errors of perception. The author proposed in an LLM dissertation [1] that, in exchange for accepting a statutory duty of candour and embracing peer review and audit, a similar defence of "non-culpable error" be adopted by the courts in English medico-legal cases where a defendant doctor has proved safe practice by audit and peer review, but has made a perceptual error, resulting finally in harm to a patient. Bringing patients who have suffered as a result of such an error within the remit of the NHS Redress scheme would seem a just and reasonable result.
Received for publication November 4, 2008. Revision received January 27, 2009. Accepted for publication January 28, 2009.
| References |
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foresight: the effect of outcome knowledge on judgment under uncertainty. J Exp Psychol 1975;1:288–99.
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