Tackling the battleground of causation: Primary versus secondary diagnoses

Zilic v QBE Insurance (Australia) Ltd [2025] NSWSC 11

In Brief

• Both a Medical Assessor and Medical Review Panel must determine what is the ‘precise battle ground between the parties’ and must adequately deal with that battle ground when providing its reasoning.
• A Medical Assessor and Medical Review Panel is not limited to identifying only a primary diagnosis. Consideration must also be given to secondary diagnoses that may have been caused by the accident, even if they are not the primary diagnoses.
• Written submissions should clearly identify and articulate all issues in dispute which form the ‘battle ground’ between the parties to ensure those issues are brought to the attention of an Assessor or Panel prior to the assessment.

Background

The Supreme Court handed down its decision in Zilic v QBE Insurance (Australia) Ltd [2025] NSWSC 11 on 4 February 2025.

The Claimant sought judicial review of a Review Panel’s diagnosis of somatic symptom disorder in respect of the Claimant’s psychological injury.

On 14 April 2024, a PIC Medical Assessor diagnosed the Claimant with an adjustment disorder with mixed anxiety and depressed mood that had arisen secondarily to an ongoing somatic symptom disorder. The Assessor assessed whole person impairment (WPI) at 19%.

On application for review by the Insurer, a Review Panel disagreed with the original Assessor’s diagnosis and findings. The Panel concluded the Claimant’s primary psychiatric diagnosis was persistent somatic symptom disorder with predominant pain and assessed whole person impairment at 0%.

The Claimant sought judicial review of the Review Panel’s decision on the following grounds:

1. The Panel only provided a primary diagnosis of persistent somatic symptom disorder with predominant pain but did not consider whether the accident materially contributed to other psychiatric diagnoses.
2. The Panel confined its consideration with respect to causation of injury to a primary psychiatric diagnosis and failed to take into account the presence of a secondary psychiatric disorder within the meaning of DSM.
3. In limiting itself to the primary psychiatric diagnosis, the Panel failed to fully exercise its jurisdiction and fell into error by asking itself the wrong question.
4. The Panel failed to properly apply clauses 1.6, 1.7 and 1.213 of the Motor Accident Permanent Impairment Guidelines (MAPIG).
5. The Panel failed to provide adequate reasoning as required under section 61(9) of the Motor Accident Compensation Act 1999 (MACA).
6. The Panel failed to provide adequate reasons as to why it disagreed with the original Assessor’s assessment and diagnosis.
7. The Panel failed to deal with a clearly articulated argument in the Claimant’s submissions, namely, that the presence of a somatic symptom disorder leading to an adjustment disorder with mixed anxiety and depressed mood does not preclude the assessment of WPI arising from the secondary adjustment disorder.

Supreme Court reasons

Justic McNaughton accepted all the Claimant’s grounds for review.

Grounds one to three and seven

Her Honour observed the Panel’s first sentence under the heading ‘diagnosis and reasons’ refers to the Claimant’s ‘primary’ psychiatric diagnosis. Her Honour accepted the Panel did not consider the substantial and clearly articulated argument centred around causation which was clearly raised in the Claimant’s written submissions, the diagnosis of the Claimant’s expert psychiatrist and the original Assessor’s Certificate. The presence of a secondary disorder was clearly articulated by the Claimant and the Review Panel was required to deal with it.

Her Honour concluded by limiting itself to the primary diagnosis and entirely failing to consider the critical issue of the secondary diagnosis when coming to its conclusion, the Review Panel failed to exercise its jurisdiction.

Ground four

Her Honour accepted the Panel failed to provide any analysis of the primary versus secondary diagnosis issue in the context of the highly relevant clauses of the MAPIG.

Grounds five to six

Her Honour noted the Panel did not explain why it came to the conclusion that the Claimant had sustained a somatic symptom disorder. The Panel simply stated it had come to that conclusion based on the material before it, its re-examination of the Claimant and that it was the most appropriate fit for the Claimant’s symptoms. Her Honour accepted, given the clear issue of a secondary psychiatric diagnosis, this approach was wholly inadequate and failed to expose the Panel’s reasoning.

Her Honour concluded the Panel failed to set out its reasons for discounting the issue of a secondary psychiatric diagnosis and disagreeing with the original Assessor’s assessment.

The Review Panel’s Certificate was set aside and the matter was remitted back to the Commission for determination by a differently constituted Review Panel.

Why this case is important

This case confirms that a Review Panel, when considering causation, must identify the specific ‘battle ground’ between the parties. It is not appropriate for a Review Panel to simply apply the same approach to each medical assessment it conducts. Rather, the Panel must tailor its approach to every matter that comes before it by clearly identifying and dealing with the issues in contention for that particular assessment and provide adequate reasoning.

Further, this case demonstrates that when diagnosing a psychological injury, there can be multiple diagnoses. A Review Panel, when determining causation, must not limit itself to identifying only a primary diagnosis. It must also consider any other secondary diagnoses that may have been caused by the accident.

Whilst this decision examined a Medical Assessor’s obligations under the MACA and MAPIG, the principles apply equally to claims under the Motor Accident Injuries Act 2017 and the Motor Accident Guidelines.