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Loss of chance: a new development in medical negligence law

James Tibballs
Med J Aust 2007; 187 (4): 233-235. || doi: 10.5694/j.1326-5377.2007.tb01207.x
Published online: 20 August 2007
Quantification of probability of loss of chance and of damages

Important questions arise regarding the quantification of the probability of a chance of a better outcome and the quantification of damages. The former is said to be quantified on the balance of probabilities — in the legal sense. Unlike causation, this does not simply mean more than 50%, nor does it mean beyond random possibility, which doctors — as scientists — might expect. The authority is the decision of the High Court of Australia in the case of Malec v JC Hutton Pty Ltd (1990),2 in which the plaintiff claimed damages for acquiring brucellosis consequent to an employer’s negligence. In assessing damages for future or potential events, the Court stated:

In other words, in the context of the balance of probabilities of a loss of chance, the probability that a chance of a better outcome existed appears, curiously, to be equivalent to the quantification of the loss of chance. Thus, a plaintiff only needs more than a 1% chance of a better outcome in order to qualify for damages, provided negligence is proven. The quantification of damages, however, is directly related to the quantification of the loss of chance in relation to the injury. It could thus be the full amount (100%) or a fraction of the value of the injury.

Development of the doctrine in Australian common law

The doctrine of loss of chance has a short medicolegal history. In several recent cases, Australian courts have established it as an alternative or additional cause of action in medical negligence litigation. Although loss of chance had earlier been recognised in the High Court of Australia as an appropriate cause of action in non-medical cases of negligence, for example in Sellars v Adelaide Petroleum NL (1994),3 and had been considered but not adopted in the medical cases Chappel v Hart (1998)4 and Naxakis v Western General Hospital (1999),5 it was determinant in the New South Wales medical case of Rufo v Hosking [2004].6 Loss of chance has subsequently been the basis of several other successful cases of negligence against doctors or health authorities in NSW, including Halverson v Dobler [2006],7 State of New South Wales v Burton [2006]8 and Tabet v Mansour [2007].9 It was also successful in Victoria, in Gavalas v Singh (2001).10 In contrast, the concept was rejected in Britain in Gregg v Scott [2005],11 and has not yet been reconsidered by the High Court of Australia. Nonetheless, it would be expected to apply in future cases in NSW and Victoria and may apply throughout Australia unless rejected in a future case before the High Court of Australia.

Rufo v Hosking [2004]6

The authority in NSW for loss of chance in medical negligence cases was established by the Court of Appeal judgment in Rufo v Hosking [2004].6

A 14-year-old girl sustained vertebral microfractures after high-dose steroids (dexamethasone was substituted for prednisolone) were used for 7.5 months for treatment of systemic lupus erythematosus, without the concurrent use of a steroid-sparing agent, such as azathioprine. She claimed damages from the medical practitioner on the grounds that the high doses of steroids caused osteoporosis and that the failure to prescribe a steroid-sparing drug deprived her of a chance of a better outcome. In the NSW Supreme Court, the trial judge ruled that prescription of the high doses of steroids was negligent but did not cause the injury — that is, causation was not established.1 He reasoned that the fractures may have occurred at lower doses, and therefore that the increase in risk with high doses was speculative. Similarly, he ruled that failure to prescribe a steroid-sparing drug did not deprive the plaintiff of a chance of a better outcome, reasoning that such a drug would have been introduced too late to prevent injury. The plaintiff’s case thus failed.

However, the decision of the trial judge was reversed on appeal and costs were allowed.6 Although the Court of Appeal agreed with the trial judge that on the balance of probabilities the defendant’s breach of duty did not cause or materially contribute to the plaintiff’s injury, the facts of the case did show, on “adopting a robust and pragmatic approach to the primary facts” and “as a matter of common sense”, that, more probably than not, the high dose of steroids did cause a loss of chance that the plaintiff would have suffered less spinal damage than she actually did. That chance was more than speculative, albeit falling short of a 51% chance.

Clarifications of the concept of loss of chance are observed in cases that followed Rufo v Hosking.

Tabet v Mansour [2007]9

In 1990, a 6-year-old child with a medulloblastoma (then unknown to treating physicians) presented to a major hospital with headaches and was admitted for several days. During this period, a varicella rash appeared. The child was discharged from hospital but re-presented to a second physician 2 weeks later with continued headaches and a resolving rash. A provisional diagnosis of meningitis was made and a lumbar puncture performed, after which the child’s condition soon deteriorated, presumably due to herniation. A computed tomography (CT) scan of the brain performed the next day revealed the medulloblastoma. Although subtotal resection was performed, followed by curative chemotherapy and radiotherapy, the child was left with severe disability.

A claim of negligence against the doctor succeeded in the NSW Supreme Court because he had breached a duty of care by not arranging a CT scan immediately after the deterioration that followed the lumbar puncture. The court ruled that causation between failure to order a CT scan and the subsequent injury was not established, but the negligence in not performing a CT scan had nonetheless deprived the plaintiff of a chance of a better outcome (avoiding brain damage). Failure to perform the CT scan was one of four possible causes of injury, the other three being tumour growth with hydrocephalus, effects of surgery, and residual effects of chemotherapy and radiotherapy. The claim was settled for $610 000, which is 40% of one-quarter of a sum of $6.1 million. If causation had been proven, the defendant would have received the full amount.

The performance of the lumbar puncture that led to neurological deterioration was argued by some testifying medical experts as contraindicated, but this was ruled not negligent. Thus, were it not for the consideration of loss of chance, the performance of the lumbar puncture may have been the only focus for a claim of medical negligence, and the court may have decided the case in favour of the defendant.

Comment

The establishment of loss of chance as a cause of action in medical negligence claims would seem to favour a plaintiff, since it is now only a question of needing to show that some chance existed of a better outcome, however small. From the other point of view, it may mean that for a defendant to succeed, it must be shown that no chance at all of a better outcome existed. The quantification of a chance of a better outcome appears to be a very low hurdle for the plaintiff, particularly if costs are allowed, and very high for the defendant. It is unlikely that a plaintiff will fail if there is any chance greater than inconsequential of a better outcome, provided negligence is proven.

These developments may have several consequences. Firstly, doctors, as defendants, may expect claims to be framed in a dual manner. A classic causation claim would address an actual adverse outcome, which on the balance of probabilities was due to the defendant’s negligent actions. In addition, a claim may now also include elements of a hypothetical chance of a better outcome, which on the balance of probabilities existed had negligence not occurred. This chance may be less than an even chance. Indeed, the chance need only be more than inconsequential.

Secondly, these changes may lead to an increase in practices of defensive medicine. Thirdly, an increase in claims may be expected, thereby offsetting benefits from recent tort law reforms, such as the imposition of caps and thresholds for general damages. Doctors’ insurance premiums may also rise.

Arguably, the quantity of lost chance should be low, otherwise an injured plaintiff has no hope of compensation unless negligence adds substantially to a naturally occurring adverse outcome. This idea was crystallised by Professor Harold Luntz:

Whatever course a plaintiff pursues — whether causation or loss of chance — in a quest for damages, an obvious need for the plaintiff to show negligence of the defendant remains. However, the requirement to show causation seems to have been substantially removed. More claims based on loss of chance can be expected, particularly when there is failure to diagnose or treat, although damages may be reduced in comparison with a successful claim based on causation.

  • James Tibballs1

  • Intensive Care Unit, Royal Children’s Hospital, Melbourne, VIC.


Correspondence: james.tibballs@rch.org.au

Acknowledgements: 

I thank Ian McKenzie and Richard Tjiong (physicians) and Margaret Kingston (legal counsel) for checking the manuscript and making valuable suggestions.

Competing interests:

None identified.

  • 1. Rufo v Hosking [2002] NSWSC 1041, 246.
  • 2. Malec v JC Hutton Pty Ltd (1990) 92 ALR 545, 549.
  • 3. Sellars v Adelaide Petroleum NL (1994) 120 ALR 16.
  • 4. Chappel v Hart (1998) 156 ALR 517.
  • 5. Naxakis v Western General Hospital (1999) 162 ALR 540.
  • 6. Rufo v Hosking [2004] NSWCA 391.
  • 7. Halverson v Dobler [2006] NSWSC 1307.
  • 8. State of New South Wales v Burton [2006] NSWCA 12.
  • 9. Tabet v Mansour [2007] NSWSC 36.
  • 10. Gavalas v Singh (2001) 3 VR 404.
  • 11. Gregg v Scott [2005] UKHL 2.
  • 12. Luntz H. Loss of chance. In: Freckelton I, Mendelson D, editors. Causation in law and medicine. Aldershot, UK: Dartmouth Publishing Company, 2002: 183-197.

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