- Consequences of injury (iatrogenic illness) (medication)
- Evidence (epidemiological)
- Jurisdiction, Tribunal (Board implicitly dealt with issue)
- Renal failure
- Significant contribution (of compensable accident to development of condition)
The worker suffered multiple injuries in August 2014, when a bobcat backed over him at a construction site. The Board granted a 49% NEL award for organic impairment and psychotraumatic disability. The worker appealed a decision of the Appeals Resolution Officer denying entitlement for renal failure.Broadly, the issue was entitlement for the worker's renal condition as a direct result of the injury or as a secondary condition. Specifically, the sub-issues were whether the injury itself caused or contributed to the onset or progression of renal failure, whether intake of medication as a result of the injury caused or contributed to the onset of the renal failure, and whether an overdose of medication in July 2009 caused or contributed to the onset of the renal failure.The standard of proof in workers' compensation proceedings is the balance of probabilities. Evidence must show more than a mere possibility of a causal connection to establish entitlement. An inference may, in certain circumstances, support a finding of significant contribution but a causation theory must have some evidence to support it; it cannot be speculative.The Panel also referred to Decision No. 600/97, the leading Tribunal case on the interpretation of epidemiological evidence in determining causation. Decision No. 600/97 stands for the general proposition that a SIR of 200 (or an odds ratio of 2) or more supports an inference of causation. When the SIR is lower, the Tribunal considers whether there are any special factors in the individual case that assist in determining whether there is sufficient evidence to support drawing an inference of causation.On the evidence, the workplace injury itself did not cause or contribute to the renal failure.Further, considering the evidence, in particular the opinion of a Tribunal medical assessor, the worker's intake of medication as a result of the injury did not cause or contribute to the renal failure. The Panel noted that the worker had been taking lithium, a known risk factor for kidney disease, for 30 years prior to the accident. He had been taking NSAIDs for only about 19 months when he required medical attention for his kidney disease; the extent of kidney dysfunction was dramatic relative to this period of intake, suggesting that it was more likely due to prolonged use of lithium. The assessor found it highly speculative to estimate to what degree the intake of NSAIDs for the compensable injury contributed to kidney dysfunction. The strongest epidemiological evidence in support of causation due to intake of medication was an elevation in risk of 1.63, well below the level required to draw an inference of causation.The worker attempted suicide in July 2009, by taking an overdose of diazepam. The Board did not explicitly consider whether this overdose contributed to the renal condition. However, the issue in the case was, broadly, whether the worker had entitlement for renal failure. Further, it has been implicitly accepted that the suicide attempt was causally related to the worker's compensable psychiatric condition. The Panel concluded that the Tribunal has jurisdiction to consider entitlement for the effects of the overdose on the worker's kidney function.The Panel accepted the opinion of the Tribunal medical assessor that the overdose probably affected the worker's renal function. The standard of proof is balance of probabilities. This opinion, that the overdose "probably" affected renal function, was not just speculative. Noting that, as a result of the overdose, the worker was diagnosed with acute renal failure superimposed on chronic renal insufficiency, the Panel concluded that the worker had entitlement to benefits for the effects of the overdose on his kidney function.The appeal was allowed in part.