PT Oakwell Pty Limited ATF Oakwell Employee Unit Trust

WORKERS COMPENSATION - Workplace Injury Management and Workers Compensation Act 1998; review of Medical Assessment Certificate (MAC); appeal against 8% assessment for psychological injury; whether computation error; whether error in making one-tenth deduction; whether adequate reasons given; Held - computation error conceded; result would be 15% whole person impairment (WPI) reduced to 14% by one-tenth deduction; Medical Assessor applied and discussed Chapter 11.10 of the American Medical Association Guides to the Evaluation of Permanent Impairment, 5th ed (AMA 5) in making one-tenth deduction; conflicting authority of Marks v Secretary, Department of Communities and Justice (No 2), Camden Council v Harle, and Matheson v Baptistcare NSW & ACT considered and discussed; observations made as to difficulties in interpretation of Chapter 11.10 and section 323; MAC revoked to correct computation error.

1. On 23 June 2025 the appellant, Kathryn Messina, lodged an Application to Appeal Against the Decision of a Medical Assessor. The medical dispute was assessed by Dr Michael Hong, a Medical Assessor, who issued a Medical Assessment Certificate (MAC) on 2 June 2025.
2. The appellant relies on the following grounds of appeal under s 327(3) of the Workplace Injury Management and Workers Compensation Act 1998 (the 1998 Act):
   • the assessment was made on the basis of incorrect criteria, and
   • the MAC contains a demonstrable error.
3. The delegate is satisfied that, on the face of the application, at least one ground of appeal has been made out. The Appeal Panel has conducted a review of the original medical assessment but limited to the ground(s) of appeal on which the appeal is made.
4. Rule 128 of the Personal Injury Commission Rules 2021 (the PIC Rules) and Procedural Direction PIC7 - Appeals, reviews, reconsiderations and correction of obvious errors in medical disputes set out the practice and procedure in relation to the medical appeal process under s 328 of the 1998 Act. An Appeal Panel determines its own procedures in accordance with r 128(1) of the PIC Rules.
5. The assessment of permanent impairment is conducted in accordance with the SIRA NSW Workers Compensation Guidelines for the Evaluation of Permanent Impairment, 4th ed

1 March 2021 (the Guidelines) and the American Medical Association Guides to the Evaluation of Permanent Impairment, 5th ed (AMA 5). "WPI" is reference to whole person impairment. "Baseline WPI" is a reference to the total WPI assessed before deduction for the effect of pre-existing injury, condition or abnormality pursuant to s 323 of the 1998 Act.

1. On 7 May 2025 this matter was referred to the Medical Assessor for a WPI caused by a psychiatric/psychological disorder on a deemed date of 17 September 2023. Ms Messina had been employed by the respondent for about 12 years. Up to April 2023 she did not encounter any problems, but at that time her previous boss left and four workers were brought in from a different company and poorly treated Ms Messina.
2. The Medical Assessor assessed 8% WPI.

1. The Appeal Panel conducted a preliminary review of the original medical assessment in the absence of the parties and in accordance with the Procedural Direction PIC7.
2. As a result of that preliminary review, the Appeal Panel determined that it was not necessary for the worker to undergo a further medical examination because the conceded error by the respondent related to an arithmetical calculation and no error was otherwise found.

1. The Appeal Panel has before it all the documents that were sent to the Medical Assessor for the original medical assessment and has taken them into account in making this determination.

1. The parts of the medical certificate given by the Medical Assessor that are relevant to the appeal are set out, where relevant, in the body of this decision.

1. Both parties made written submissions which have been considered below by the Appeal Panel.

1. The procedures on appeal are contained in s 328 of the 1998 Act. The appeal is to be by way of review of the original medical assessment but the review is limited to the grounds of appeal on which the appeal is made.
2. In Campbelltown City Council v Vegan[1] the Court of Appeal held that the Appeal Panel is obliged to give reasons. Where there are disputes of fact it may be necessary to refer to evidence or other material on which findings are based, but the extent to which this is necessary will vary from case to case. Where more than one conclusion is open, it will be necessary to explain why one conclusion is preferred. On the other hand, the reasons need not be extensive or provide a detailed explanation of the criteria applied by the medical professionals in reaching a professional judgement.

1. In calculating the median class the Medical Assessor produced the following chart:

Her social functioning, travel and self-care are improved since increased antidepressant and psychologist treatment, with significant elimination of her psychiatric impairment.

1. In recording details of any previous or subsequent accidents common injuries or condition, the Medical Assessor said:

"In terms of past psychiatric history, I began by discussing that I have read her records and noted a pre-accident psychiatric history. Ms Messina said she divorced many years ago, around 20 years ago. She was on Fluvoxamine 50mg for 20 years. She said it helped her "stabilize" and when she ceased it, which was not long, she did not feel "even keel" and she felt she could manage life better and function better. She could not remember more about how she was before treatment commenced."

1. The Medical Assessor recorded the following present treatment:[2]

"Ms Messina has been consulting Colette Mills, psychologist, recently every 3-4 weeks, since 2024. She said she saw a psychologist from Navigator, a psychology service via telehealth in early 2024 with no benefit.

Fluvoxamine antidepressant, gradually increased over time and she has been on 200mg for 4-5 months now. On increased dose, she said she sleeps better, her anxiety is less and she can do more.

1. In his summary at [7] of the MAC the Medical Assessor said:

In summary, Ms Messina has a history of depression and anxiety symptoms and maintained Fluvoxamine 50mg for many years and was on antidepressant when the injury happened. Without the medication, she did not function very well and therefore went back on medication.

Due to the issues at work which persisted for five months, she developed depression and anxiety symptoms which likely reached the level of Major depressive disorder.

After increasing the same antidepressant, and having further psychological treatment, she has improved and her psychological injury is stabilised now, and MMI has been reached."

1. In considering other reports at [10c] of the MAC the Medical Assessor noted in discussing

"...She discussed Dr Khan's assessment with 18% and also a report from Dr Cocker but does not agree with that, because her medication had increased since September 2023 to 150 mg, and she does not believe she should be required to take a higher dose (Comment: although I noted that even though the statement was dated April 2025, she said her dose had increased to 200mg more than 4-5 months now, with benefit)."

1. In discussing the opinion of Ms Messina's expert, Dr Abdal Khan, the Medical Assessor noted that Ms Messina had denied any pre-existing psychiatric history. He commented:[3]

"Dr Abdal Khan IME psychiatrist's report dated 24 October 2024 noted a similar problem with work and that Ms Messina experienced poor sleep, appetite and weight disturbance, and impaired concentration (Comment: he did not record how much weight she lost, and she told me it was no more than1 or 2kg). She denied pre-existing psychiatric history (Comment: which is inconsistent with other records and could be wrong) and was on Fluvoxamine, 150mg. He diagnosed Major depressive disorder and Generalized anxiety disorder and advised that her condition is stabilised and provided WPI 232234, which came to 17% before adding 1% for treatment uplift with no explanation.

It should be noted that Ms Messina was probably not MMI at that time, given that the recorded function is quite different and her antidepressant has further increased with benefit."

1. In considering the report of Dr Ryan Cocker, the Medical Assessor noted that he had taken a history of mild anxiety 25 years ago and that Ms Messina had been on Fluvoxamine.
2. In commenting on Dr Cocker's report the Medical Assessor said:

"(Comment: I noted that Ms Messina has since improved with increasing medication, she does not get lost when out, and has good relationship with her friends and children now)."

1. In discussing the deduction he made of 10% the medical assessor said at [11]:

"11. DEDUCTION (IF ANY) FOR THE PROPORTION OF THE IMPAIRMENT THAT IS DUE TO PREVIOUS INJURY OR PRE-EXISTING CONDITION OR ABNORMALITY

1. In my opinion the worker suffers from the following relevant previous injuries, pre-existing conditions or abnormalities:

(i) There was a pre-existing condition, which was consistent with an Adjustment disorder with anxiety and depressive symptoms.

(ii) Ms Messina's pre-existing condition contributed to her current impairment, because Ms Messina was on treatment at the time of the work injury, and there was psychiatric impairment ascertainable before the work injury, according to the chapter 11.10 of the Guides. Because of the previous psychiatric condition, her current impairment is greater overall. Had Ms Messina not had the previous psychiatric condition and previous impairment, the current WPI would not have been as great.

1. I have considered assessing Ms Messina's pre-existing PIRS according to chapter 11.10 of the Guides, however, as Ms Messina could not recall her impairment well before the subject injury, and there are insufficient objective evidence or contemporaneous records, my view is the percentage of pre-existing impairment cannot be assessed with a PIRS and I have assigned 10% of the total WPI to the pre-existing impairment, as recommended by the Guides. As a further consideration, if Ms Messina's pre-existing condition was in remission because of treatment as reported, then the pre-injury PIRS was 0%, with 3% treatment uplift for total elimination of impairment as a result of long-term effective treatment, and without antidepressant, the pre-existing impairment had reverted to original impairment, and this means the total WPI before work injury, was 0+3=3%. She said she tried but could not stop Fluvoxamine, and did not function well without it.

In the alternative, if s323(2) of the Act were to be applied, then I consider the extent of the deduction is difficult and costly to determine, and I assess the deductible proportion as one-tenth for a pre-existing injury. This is not at odds with the available evidence, as the pre-existing psychiatric disorder does contribute to the current impairment and the current impairment would have been as greater, were it not for the pre-existing psychological condition, but this is only a minor contribution."

1. The first issue raised by Ms Messina was that the Medical Assessor had incorrectly applied the guidelines in assessing her WPI.
2. This point was conceded by the respondent.
3. The second issue was that the Medical Assessor had erred in his application of s 323 of the 1998 Act. We were referred to Cole v Wenaline Pty Ltd[4] and the well-known analysis by Schmidt J with regard to the application of the section. We were also referred to Ryder v Sundance Bakehouse.[5]
4. Ms Messina submitted that there had been a misapplication of s 323 as the Medical Assessor had actually concluded that the contribution to the baseline impairment was 0%.
5. Ms Messina submitted:[6]

"20... . The worker was taking anti-depressants, so her impairment was at 0%, and

therefore, there was no addition to the impairment causally related to the subject

1. Ms Messina argued that a 0% impairment did not make the baseline impairment worse, and that therefore the deduction of 10% constituted an error. We were referred to Southwell v Qantas Airways Limited[7] to the unremarkable effect that if there is no evidence establishing a contribution to the baseline assessment, then no deduction could be made under s 323.
2. The alternative hypothesis advanced by the Medical Assessor, Ms Messina argued, demonstrated that s 323 was inapplicable. She said "It is not clear who [the Medical Assessor] was hypothesising would make the deduction.
3. Ms Messina said s 323(2) either applied or it did not.
4. It was submitted that in view of the Medical Assessor's conclusions the section did not apply, as he had already concluded that the contribution was 0%. It was not difficult therefore to determine the extent of the contribution because he had already assessed and determined it as being at 0%.
5. Thirdly, Ms Messina argued that the Medical Assessor had failed to provide adequate reasons, relying on Vegan, which we have referred to above.
6. This submission covered both the mathematical error to which we have referred and also the reasons given by the Medical Assessor governing his determination regarding s 323.

1. As noted above, the respondent conceded that there had been a mathematical error in determining the appropriate median score.
2. The respondent submitted that applying the relevant provisions of Chapter 11, the entitlement would nonetheless result in a total of 14% WPI which would not entitle Ms Messina to a payment of lump sum compensation.
3. The respondent submitted that a median class score of 3 together with an aggregate class score of 14 would have resulted in an entitlement to 13% WPI on a proper application of Chapter 11.14. The Medical Assessor had added 2% WPI for the effects of treatment (which the respondent did not challenge).
4. The respondent noted that, whilst that would entail a finding of 15% WPI, after the deduction of 10% found for pre-existing factors, Ms Messina's entitlement would remain at 14%.
5. In responding to the submissions regarding s 323, the respondent also referred to Cole and to Ryder.
6. The respondent observed that the Medical Assessor did not in fact find that there was a 0% contribution, but indeed specifically stated that if Ms Messina had not had the previous psychiatric condition and impairment, then her current her WPI would not have been as great. The reference to 0% was the Medical Assessor's alternative view, were it the case that Ms Messina had been in remission as she had alleged.
7. The assessment by the Medical Assessor of 10% was, it was submitted, based on the absence of sufficient objective and contemporaneous evidence, which made it difficult and costly for the Medical Assessor to determine the contribution.
8. As to the submission that the Medical Assessor had failed to give adequate reasoning for his decision regarding the application of s 323, the respondent submitted that in explaining that Ms Messina was unable to recall the extent of her impairment prior to the subject injury and in the absence of sufficient objective and contemporaneous evidence to establish its extent, he had applied the provisions of s 323(2).
9. That explanation, the respondent submitted, had provided sufficient reasoning.

"11.14 Each area of function described in the PIRS is given an impairment rating which ranges from Class 1 to 5.

The six scores are arranged in ascending order, using the standard form. The median is then calculated by averaging the two middle scores eg:

Example B: 1, 2, 2, 3, 3, 4 Median Class = 2.5 = 3*

*If a score falls between two classes, it is rounded up to the next class. A median class score of 2.5 thus becomes 3."

1. It can be seen that the application of the guideline, given the scores entered by the Medical Assessor, should in fact have been in accordance with example B - that is to say, 2.5 which would give a median class of three.
2. Using the conversion table at Table 11.7 of the Guidelines that would have entitled Ms Messina to a finding that she suffered from 13% WPI.
3. The Medical Assessor further modified his assessment by applying the provisions of Chapter 1.32 of the Guidelines to allow a further 2% WPI for the effects of treatment.
4. As submitted by the respondent, that would entitled Ms Messina to a 15% WPI, but from it the deduction of one-tenth would have resulted in an entitlement of 14% WPI.

1. The challenge to the one-tenth deduction was based, with respect, on a misunderstanding of the explanation given by the Medical Assessor for his decision.
2. Section 323 of the 1998 Act provides relevantly:

"(1) In assessing the degree of permanent impairment resulting from an injury, there is to be a deduction for any proportion of the impairment that is due to any previous injury (whether or not it is an injury for which compensation has been paid or is payable under Division 4 of Part 3 of the 1987 Act) or that is due to any pre-existing condition or abnormality.

(2) If the extent of a deduction under this section (or a part of it) will be difficult or costly to determine (because, for example, of the absence of medical evidence), it is to be assumed (for the purpose of avoiding disputation) that the deduction (or the relevant part of it) is 10% of the impairment, unless this assumption is at odds with the available evidence."

1. As noted above the Medical Assessor gave his assessment using the provisions of Chapter 11.10 of the Guidelines. This provides:

11.10 To measure the impairment caused by a work-related injury or incident, the psychiatrist must measure the proportion of WPI due to a pre-existing condition. Pre-existing impairment is calculated using the same method for calculating current impairment level. The assessing psychiatrist uses all available information to rate the injured worker's pre-injury level of functioning in each of the areas of function. The percentage impairment is calculated using the aggregate score and median class score using the conversion table below. The injured worker's current level of WPI% is then assessed, and the pre-existing WPI% is subtracted from their current level, to obtain the percentage of permanent impairment directly attributable to the work-related injury. If the percentage of pre-existing impairment cannot be assessed, the deduction is 1/10th of the assessed WPI.

1. At [11b(i)] of the MAC the Medical Assessor found that there was a pre-existing condition that did contribute to the baseline impairment. As shown above, he took a thorough and careful history, including a finding that the dosage had recently been increased of Ms Messina's

20-year use of Fluvoxamine. He found that Ms Messina was already under treatment at the time of the work injury, a fact that has not been challenged. This triggered the above provisions of Chapter 11.10, but at paragraph [11c] the Medical Assessor went on to explain that he was not able to construct a pre-injury psychiatric impairment rating scale (PIRS) because there was "insufficient objective evidence or contemporaneous records" to enable him to do so. 2. He further pointed to a difficulty in applying the provisions of Chapter 11.10 in any event. Ms Messina's treatment prior to her injury meant that although she had an impairment for the purposes of the calculation of the pre-injury PIRS, it could not be taken into account because her Fluvoxamine medication had the effect of disguising the pre-existing condition and would have thus given a false reading. The pre-injury PIRS thus would have to have shown 0% contribution from her pre-existing condition when the same condition contributed to the baseline impairment caused by the subject injury. 3. The Medical Assessor's view was that 3% WPI would have been assessed for Ms Messina's condition before she suffered the subject injury, but for the application of the treatment effect modifier, which is in a separate chapter to Chapter 11, namely Chapter 1.32. It can be seen that Chapter 11.10 provides that the pre-existing WPI "is subtracted from their (sic) current level" which level is used "to obtain the percentage of permanent impairment directly attributable to the work-related injury." On one reading, that would require a 3% deduction from the baseline assessment, leaving a 12% WPI total.

1. The provisions of Chapter 11.10 have been criticised and indeed declared to be invalid, although there is now some curial debate in that regard. In Matheson v Baptistcare NSW & ACT[8] Basten AJ distinguished the decision of Simpson AJ in Marks v Secretary, Department of Communities and Justice (No 2).[9]
2. Chapter 11.10 was further considered in a Medical Appeal Panel case, Camden Council v Harle[10], where the whole of Chapter 11.10 was considered to be invalid, but was not cited in the above cases.
3. As can be seen from the above, the interpretation of Chapter 11.10 is not without its difficulties and certainly not without its complexities. It is clear that, with respect, Ms Messina did not fully appreciate the context in which the Medical Assessor made his comments, as there was no reference to Chapter 11.10 in her submissions.
4. In Matheson, Basten AJ held that, contrary to the decision in Marks No 2, Chapter 11.10 was not invalid, as consideration had not been given to the "distinctions drawn within the Workers Compensation Acts as to the treatment of psychological and other injuries, and thus omits inferences to be drawn from the legislative scheme" (at [32]). In Marks No 2 Simpson AJ had found that to the extent that Chapter 11.10 precluded the assessment of impairment from a previous injury which was asymptomatic, it was inconsistent with the causative element of

s 323 and was therefore invalid. 5. In distinguishing Marks No 2, Basten J said from [22]:

"22. There are authorities in this Court and in the Court of Appeal holding that s 323(1) of the Workplace Injury Act requires a causal connection between a

pre-existing injury, condition or abnormality and the impairment arising from the injury the subject of the claim. That is, there is to be a deduction where any proportion of the impairment 'is due to' any previous injury, condition or abnormality. The deduction is not contingent upon a finding that the previous injury itself caused an impairment. Accordingly, an asymptomatic injury which contributes to the present impairment must result in a deduction.

1. However, all but one of the cases was concerned with physical injury: only one, to be addressed below, involved a psychological injury. Although s 323 does not distinguish between physical and psychological injuries, other parts of the Workers Compensation Acts do make such a distinction. [His Honour then referred to s 65A of the 1987 Act]. There is thus no a priori reason for assuming that a general provision such as s 323 of the Workplace Injury Act necessarily applies in the same way to each category of injuries."
2. From [25], His Honour stated:
   1. "It is, of course, true that the Guidelines cannot, of their own force, vary the substantive effect of the Acts. However, the Guidelines do not operate of their own force in that manner: their operation is given mandatory statutory effect, in general terms by s 322(1) and, specifically in relation to the calculation of a pre-existing condition, by s 323(4). There is no reason in principle why those two provisions cannot give effect to a guideline which, in a particular respect, qualifies the substantive effect of s 323(1).
   2. Further, as has been explained by reference to the detailed and, in one sense, artificial, structure imposed by the Guidelines on the assessment of 'permanent impairment' with respect to psychological injuries, the degree of permanent impairment has no content separate from the numerical value mandated by application of the Guidelines."
3. His Honour stated that the concept of an asymptomatic psychological condition differed from that of an asymptomatic physical injury and said at [27]:

"27 .....Thus, the PIRS used to assess permanent impairment from psychological injuries is entirely based on behavioural factors, as compared with the guidelines dealing with physical injury which require assessment of physical conditions, such as reflexes, hearing loss and the results of radiological investigation.

1. Thus, where the impairment caused by a psychological injury is to be assessed by reference to behavioural elements, it makes sense that any reduction in the numerical result of that assessment should be made by reference to behavioural elements."

1. The basis of the Medical Assessor's finding that there was a pre-existing condition which contributed to the baseline assessment was that she had been taking Fluvoxamine for her adjustment disorder for 20 years.
2. He also found that the application of s 323(2) was not at odds with the available evidence, as he explained when considering the reports of Dr Khan and Dr Cocker.
3. Dr Khan reported on 23 October 2024[11]and found that there was no pre-existing condition as he took a history that there had been none.[12]
4. Dr Ryan Cocker, reporting for the respondent on 10 February 2025 noted:[13]

"Kathryn describes chronic and fluctuating symptoms of mild anxiety since her divorce 25 years ago. She reports that these occurred for a few days every couple of months. She took an SSRI antidepressant, fluvoxamine, sporadically over several years prior to her psychological injury. She did not have psychological treatment. She reports that these symptoms were well-controlled prior to this psychological injury and there was no evidence of any functional impact."

1. The Medical Assessor noted that Ms Messina's condition had improved with the increase in her dosage to 200mg from 150mg, which began some four to five months prior to

2 June 2025, the date of the MAC. Dr Cocker's report was dated 10 February 2025.

1. We note that Ms Messina has not challenged the Medical Assessor's assumptions that she had been on antidepressant medication for many years prior to her injury, or that she was taking the medication at the time she commenced her employment with the respondent.
2. The effect of the decision in Matheson is that it must be assumed that an inference is to be taken that in cases of psychological injury, the application of s 323 is to be governed by a separate scheme provided by Chapter 11.10. Basten AJ stated at [34]:

"....A precondition to the operation of s 323(1) is that a causal connection can be established between a previous injury and the existing state of impairment. There is no inconsistency between the terms of sub-s (1) and a guideline which states how that pre-condition may be satisfied...."

1. A synopsis of the reasons given by the Medical Assessor shows:
   • the Medical Assessor found that but for her previous adjustment disorder, Ms Messina's current baseline WPI would not have been as great;
   • in accordance with Chapter 11.10, he then turned to the construction of a pre-injury PIRS, but was unable to do so as there was insufficient "objective evidence or contemporaneous records" - which we take to mean "available information" in Chapter 11.10 terms - on which to base a rating;
   • if there had been enough available information to enable the Medical Assessor to construct a pre-injury PIRS, then in applying the whole of Chapter 11.10, he would have found that the pre-existing condition contributed 3% WPI to the pre-injury baseline WPI. However, if the Chapter 1.32 treatment modifier were applied, the pre-injury s 323 deduction would have been 0%, as Ms Messina's treatment had resulted in total elimination of impairment, but without which she would have reverted to her original impairment;
   • he therefore assigned 10% in accordance with the last sentence in Chapter 11.10, namely "If the percentage of pre-existing impairment cannot be assessed, the deduction is 1/10th of the assessed WPI";
   • thus, if he did not take the effect of treatment modifier into account, there would have been a 3% deduction to the pre-injury PIRS, had he had enough information on which to base such a calculation, and
   • alternatively, pursuant to s 323(2), he found that the extent of the pre-existing condition would be difficult and costly to determine.
2. We are satisfied that the Medical Assessor's comments about what he would have done had there been sufficient available information, whilst informative, are of no assistance in the resolution of this dispute. They illustrate another potential problem with this particular guideline, but his finding that there was insufficient information would appear to be the reason he utilised the Chapter 11.10 assumption of a one-tenth deduction, as the

pre-injury PIRS could not be assessed. We note that there has been no challenge to the latter finding. 3. What is unclear from this synopsis, is whether the application of Chapter 1.32 is applicable in the construction of a Chapter 11.10 PIRS. Chapter 1.32 provides:

"1.32 Where the effective long-term treatment of an illness or injury results in apparent substantial or total elimination of the claimant's permanent impairment, but the claimant is likely to revert to the original degree of impairment if treatment is withdrawn, the assessor may increase the percentage of WPI by 1%, 2% or 3%. This percentage should be combined with any other impairment percentage, using the Combined Values."

1. A question which then arises is whether this guideline can of its own force, vary the substantive effect of the Workers Compensation Acts. It has the effect of varying the substantive force of s 323 by its application to a different guideline, Chapter 11.10, as it prevents an otherwise appropriate deduction from being made.
2. Finally, the provisions of Chapter 11.8 provide:

11.8 Consider the effects of medication, treatment and rehabilitation to date. Is the condition stable? Is treatment likely to change? Are symptoms likely to improve? If the injured worker declines treatment, this should not

affect the estimate of permanent impairment. The psychiatrist may make a comment in the report about the likely effect of treatment or the reasons for refusal of treatment."

1. Whether there is an inference available that links Chapter 1.32 with this guideline is a moot point. On the one hand there is no specific reference to the modifiers in either Chapter 11.8 or Chapter 11.10, and on the other, Chapter 11.8 is not part of the inferential modification to s 323 provided by Chapter 11.10, as has been found in Matheson. The resolution of these matters must abide a further decision, but in the present case, whilst acknowledging the wide ranging issues raised by the Medical Assessor in [11] of the MAC, we consider that the finding that there was insufficient information to construct a pre-injury PIRS was an adequate, if not compelling, reason for his using the assumption provided in Chapter 11.10 of a 1/10th deduction. If we are wrong in that finding, we would simply apply the statutory assumption provided by s 323(2).
2. For these reasons, the Appeal Panel has determined that the MAC issued on 2 June 2025 should be revoked to reflect the computation error, and a new MAC should be issued. The new certificate is attached to this statement of reasons.

PT Oakwell Pty Limited ATF Oakwell Employee Unit Trust

This Certificate is issued pursuant to s 328(5) of the Workplace Injury Management and Workers Compensation Act 1998.

The Appeal Panel revokes the Medical Assessment Certificate of Medical Assessor Michael Hong and issues this new Medical Assessment Certificate as to the matters set out in the Table below:

Chapter, page and paragraph number in NSW workers compensation guidelines

Chapter, page, paragraph, figure and table numbers in AMA 5 Guides

Proportion of permanent impairment due to pre-existing injury, abnormality or condition

Sub-total/s % WPI (after any deductions in column 6)

Total % WPI (the Combined Table values of all sub-totals)

[1] [2006] NSWCA 284.

[4] [2010] NSWSC 78.

[5] [2015] NSWSC 526.

[7] [2024] NSWSC 497.

[8] [2025] NSWSC 213.

[9] [2021] NSWSC 616.

[10] [2022] NSWPICMP 339.