CALCULATION OF MEDICAL RELATED ASTHMA COSTS

1.1 Pharmaceuticals

The Australian annual wholesale sales figure (June 1991) for each of the major asthma therapeutic drug groupings and devices was obtained from IMS Australia Pry Ltd. This figure was adjusted for chemist markup (10%) and government dispensing fees to give a price to consumer value. It is realised that different parts of Australia have different regulations concerning the supply of some beta₂ agonist preparations and as a result dispensing fees may vary. However, the overall impact of these 'fee' differences is marginal and a standard fee of $3.43 per prescription has been used. Hospital prescribed medications and devices are excluded from the figures as these were captured in hospital costs¹⁴. The cost of nebulisers have also been excluded because of a lack of available reliable data.

The percentage of drug sales prescribed specifically for the treatment of asthma, rather than other respiratory conditions, was provided by the Australian Medical Index (AMI). The AMI is an ongoing morbidity survey conducted by IMS Australia for the pharmaceutical industry. The survey is based on the prescribing patterns of a stratified random sample of GPs. Participants are provided with a modified prescription pad so that a copy of each patient prescription can be returned to IMS. This provides information on patient demographics and diagnoses as well as the type and dose of medications used to treat each diagnosis.

Figure One provides a breakdown of the total pharmaceutical cost.

1.2 Medical Consultations

A calculation schemata of the total medical consultation cost for asthma is shown in Figure Two. Total GP and specialist consultation fees for all diseases, $1,801 million and $792 million respectively, were obtained from Department of Health, Housing and Community Services (DHHCS) 1990/91 attendance statistics.

A weighted average cost per GP/specialist consultation for all diseases of $25.96 was calculated by dividing the relevant total cost figure by the corresponding number of visits to GPs (84.9 million) and specialists (14.9 million).

The proportion of asthma related medical consultations was imputed from the actual number of GP asthma consultations of 3.2 million (IMS) and the ratio of GP to total consultations of 0.85 (DHHCS). This provided the best estimate for the total number of asthma related medical consultations of 3.76 million. The total cost to the community for asthma related consultations is therefore estimated at around $98 million for 1990/91.

The finding by the ABS 1989/90 National Health Survey that Australian asthmatics made some 128,600 visits to medical practitioners in a two-week period (the equivalent of 3.4 million consultations annually) was not included because it lacked statistical significance and a more accurate source was available.

1.3 Hospital

Calculation details for the total annual cost of asthma related hospitalisations of $59 million are included in Figure Three. This calculation is based on average hospital costs.

The average cost of a public hospital bed day of $388 was obtained from unpublished Australian Institute of Health (AIH) 1990 data and inflated by the AIH hospital and clinical deflator. The cost of a private hospital bed day of $303 is also an inflation adjusted figure sourced from the 1990 review of private hospitals by the Australian Health Ministry Advisory Council (AHMAC). The private hospital bed day cost of $303 does not include pharmaceutical costs. ABS State Morbidity data was used to calculate a ratio of private to public admissions of 8:1 to derive the weighted average cost of a hospital bed day of $379.

Multiple sources were reviewed for estimating asthma related bed days. The Australian Institute of Health's 1990 estimate of 155,000 bed days for asthma was adopted because the source is reputable, relatively current and is based on actual statistics. The figure is also confirmed by South Australian Health Commission population adjusted bed day figures of 150,000 days for asthma in the same time period. A higher estimate of 262,000 bed days from the ABS 1989/90 National Health Survey was excluded because of high sampling variability. The ABS figure also included all people admitted to hospital who listed asthma as one of a number of reasons for admission and as such may overestimate asthma related bed days.

Ideally, specific Diagnostic Related Group (DRG) bed day costs for asthma should be used to calculate the costs of hospitalising asthmatics. Unfortunately, at the time of the study these costs were not available with sufficiently reliable utilisation data to be included.

1.4 Allied Health Treatment Costs

Allied health treatment costs represent the cost of asthmatics visiting all other health professionals, excluding pharmacists, and are estimated at close to $8 million for 1991. The estimate has been derived as per the schemata in Figure Four and is based on current asthma related allied health treatment usage trends (ABS 1989/90 National Health Survey) and inflation adjusted cost data. The average cost for an allied health treatment consultation was derived from a survey of relevant professional associations.

1.5 Ambulance

The total number of ambulance responses to asthmatics was determined by adjusting asthma call-out data collected by the NSW Ambulance Service by an ABS 1991 Australian/NSW population ratio. This national volume of ambulance responses for asthma was multiplied by the average cost per NSW ambulance response (a 1987/88 figure inflated by the AIH hospital and clinical deflator) to give a total Australian ambulance cost for asthma of $4.9 million. The calculation schemata is included in Figure Five.

¹⁴ Private hospital pharmaceutical usage is mostly absorbed in the pharmaceutical cost section. Unfortunately, at the rime of this research. insufficient data was available to capture the total private hospital pharmaceutical usage.

Content Updated 1992