Determining Impairment using the Occupational Asthma Guidelines
The occupational asthma guidelines1 were developed and published in July 2006 to address the then widespread concerns that application of the American Medical Association Guides to the Evaluation of Permanent Impairment 4th edition (3rd printing) did not allow for a fair and reasonable assessment of impairment in persons suffering from occupational asthma. For example, criticisms, such as low impairment scores in persons whose relatively normal lung function tests were achieved only at the cost of significant medication taking, were common. Since their introduction, the Guidelines have been widely used in matters covered by the Wrongs Act 1956 (Vic) and the Workers Compensation Act 1985 (Vic).
In recent months it has become clear that there is some confusion regarding the method to be applied to assessing the four descriptors (respiratory function tests, clinical, treatment, and exercise capacity) and how they are used to arrive at an overall impairment score. This matter has been the subject of a complaint by a worker’s legal representative. It has also been noted by WorkSafe agents that there is inconsistency in the approach used by independent impairment assessors in applying the four descriptors.
Inconsistency or lack of understanding as to how the overall whole person impairment class and percentages are derived makes it difficult for the worker, their legal representatives and the claims agent to verify whether the assessment has been performed in accordance with the way the authors of the occupational asthma guidelines intended. Although not many in number, parties to the claim are more likely to refer the matter to a Medical Panel or in the case of a claims agent, modify the impairment assessment in accordance with section 104B (2A) of the Accident Compensation Act 1985 (Vic).
To date, the inconsistencies involve the following approaches in determining the level of impairment:
- Basing the class of overall whole person impairment on the descriptor (respiratory function tests, clinical, treatment or exercise capacity) with the highest value
- Estimating the overall whole person class of impairment with a weighting on the respiratory function test descriptor
- Using the median class to determine overall whole person impairment
- Using the respiratory function test descriptor to determine the overall class and using the other descriptors (clinical, treatment or exercise capacity) to determine the impairment percentage level within that class.
Whilst the occupational asthma guidelines do not provide any specific instructions regarding their interpretation and the method of determination of respiratory impairment in persons with occupational asthma, it was the intention of the working party providing advice to the authors that the following methodology be used –
- Chose the impairment class of the worst of the four descriptors (respiratory function tests, clinical, treatment or exercise capacity).
- Determine the actual impairment score from the range of impairment scores within that class (eg Class 3, 10-29%) based on the severity, for example, of the symptoms within the impairment class.
- The score may be further adjusted up or down according to the severity of another descriptor or descriptors. For example, if the score for another descriptor falls into a class immediately below or even in the same class, then a score in the upper part of the range should be selected (e.g. for Class 3, 20-29%).
- The assessor should be mindful of the caveat regarding exercise capacity. If this descriptor provides the worst score (Impairment Class), it should only be accepted as such provided there is no other cause for the limitation in exercise capacity (e.g., cardiac disease). If the exercise capacity is to be discounted because the impairment assessor is of the opinion that the associated breathlessness is due to another condition then it is important to provide evidence, historical, clinical or otherwise, to that effect. In this regard the measurement of maximum oxygen uptake (VO2(max)) can be helpful.
This methodology in determining the impairment score using the occupational asthma guidelines is appropriate for two reasons. Firstly, it is what the authors and Advisory Committee intended. Secondly, it is the same methodology used in determining impairment when using Table 8 on page 5/162 of the AMA4 (3rd printing) Guides where impairment is determined by selecting the impairment class into which the respiratory physiological measurement falls and then making a value judgment regarding severity within the class.
Respiratory Reference Group
1. Streeton Jonathan, Burdon Jonathan, Pain Michael. Impairment Assessment in Workers with Occupational Asthma. Victorian Government Gazette 2006;G30:1580-1586.
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