Quantitative component 99 !

This project demonstrated a sustained improvement in the P : R ratio for at least 12 months after the intervention. It has been shown that the P : R ratio can be applied as a surrogate measure to assess the quality of prescribing for asthma, and is an important factor related to asthma morbidity.129,318 An increased P : R ratio has been associated with improved asthma symptoms,318 reduced need for rescue courses of oral prednisolone,129 and reduced emergency department visits,316 hospital admissions319 and urgent GP visits.317

There has been other studies examining asthma management which have used the number of canisters130,131 or defined daily doses129,319 as a measure of ICS use. The limitation of using the number of canisters is that it does not account for the number of doses per canister or differing drug potencies, whereas a limitation of using defined daily doses is the poor representation of the widely accepted dose equivalence. A particular strength of this study is the fact that the potencies and doses per canister were

It has previously been demonstrated that dispensing of medium-to-high level ICS therapy is associated with a reduced risk of ICU admission, whereas high level inhaled SABA dispensing is associated with an increased risk of both ICU admission and endotracheal intubation for asthma.131 Importantly, stratified analysis indicated that this excess risk is observed only among patients not receiving ICS therapy.131 Therefore, the increased P : R ratio reported by this project should be interpreted with caution. Despite the fact that the P : R ratio was the primary outcome measure used in this project, further analyses were necessary in order to determine whether the increase in the P : R ratio resulted from an increased preventer usage or a decreased reliever usage, before any conclusions could be drawn.

Further analysis found that the increased P : R ratio was largely due to a reduction in the average daily use of reliever medication. A number of international studies have demonstrated improved asthma outcomes with decreased reliance on reliever medications.325-327

The average salbutamol-equivalent daily usages of SABA ranged from 218.6 #g to 655.7 #g, which is equivalent to 2-6 puffs per day, over the study period. Unfortunately, this range of daily SABA consumption is well above what is recommended by the NAC and Asthma Foundations Australia, who state that usage of reliever medication on three or more occasions per week is indicative of suboptimal asthma control.59,328 According to Australian asthma management guidelines, and assuming all dispensed medication had been consumed, patients using this quantity of reliever medication should be classed as having poor asthma control, and should be receiving regular ICS therapy.59 The assumption that dispensing correlates with medication use was a limitation of this study, as discussed later.

While it was encouraging to see a sustained improvement in the P : R ratio and decrease in reliever usage, it was somewhat disappointing that the usage of ICS did not increase over the study period. The median beclomethasone-HFA equivalent daily usage of ICS over the study period fell within or below the ‘low dose’ range according to the NAC.59 Assuming all dispensed medication had been consumed, the average daily usage of SABA reported over the study period indicated that the majority of patients analysed would be classified as having poor asthma control, and should therefore be maintained

on moderate-to-high dosages of ICS, as well as a LABA.59 Unfortunately, approximately half of the patients were not using any ICS over the study period.

Inadequate use of ICS could be due to under-prescribing and/or poor adherence with therapy. It has been found that a large proportion of patients with asthma do not understand the role of their medications and have many misconceptions and fears in regard to ICS, reducing their willingness to use them.263 In addition, it has been widely demonstrated that patients prefer to manage their asthma as an acute intermittent disorder rather than a chronic ongoing disease that needs monitoring and managing.75-77 Patients’ perceptions of their condition and their need for treatment limit the adherence to ICS therapy, and therefore the reported effectiveness of ICS. Barriers to ICS use must be overcome before widespread benefits of ICS therapy are seen.

The results showed decreases in reliever usage after the intervention in Group 1, but increases in reliever usage after the intervention amongst patients in Group 2. Furthermore, the preventer usage decreased immediately after the intervention in Group 1, but increased immediately after the intervention in Group 2. While these patterns in reliever and preventer usage resulted in increases in the P : R ratios in both groups, it is important to note the effect of seasonal variation on the results. Group 1 received the intervention in late October 2006, whereas Group 2 received the intervention in late April 2007. Therefore, warmer summer months were represented in Group 1’s 0-6 month post-intervention dispensing data, and colder winter months were represented in Group 2’s 0-6 month post-intervention data. Winter months often result in poor asthma control,329,330 which may explain the differences in preventer usage from one six-month period to the next.

There are potential limitations to the quantitative component of this study. It was assumed that the dispensed quantity of reliever medication equated with actual medication consumption, but factors such as storing relievers in different sites, sharing medication with family members and misplacing medication could complicate the picture. It is also possible that non-prescription supply of relievers, which is not always recorded in the dispensing software, resulted in underestimation of reliever medication usage. Underestimation may also have arisen from the assumption that asthma

Furthermore, the research team attempted to account for this underestimation in the patient identification algorithm used by the data mining software, by being considerably generous in the quantity of relievers that indicated suboptimal management.

Not all of the patients originally included in the study were eligible for inclusion in the follow-up study. Ineligible patients either did not receive the intervention, or did not have available data at the time of follow-up. It could not be assumed that the unavailability of patent data implied that the patient was no longer using asthma medication. Thus, it was deemed more accurate to exclude these patients, avoiding skewing of the data. However, when interpreting the results presented here it should be borne in mind that the outcomes only apply to half of the patients in the original sample. Furthermore, all data were collected in one single state (Tasmania), therefore caution must be exercised in extrapolating the findings to the rest of the Australian population as there may be local effects not present in other Australian states or territories.