Persistent asthma: disease control, resource utilisation and direct costs

Two factors should be distinguished in asthma: the degree of disease severity and the level of control achieved by the patient 1. Asthma severity can be considered as an intrinsic and rather stable characteristic of the disease for a given patient, i.e. the maximal level of impairment that asthma can bring to that patient, up to and including death; it is unclear how severity is affected by therapy 2. One way to assess severity is the level of corticosteroid prescription, inhaled or oral 3. By contrast, the level of control varies with time; it is primarily determined by contacts with allergens or infectious agents, and by therapy 4. In theory, the level of control can be influenced by patients, since they may influence two determinants of control, i.e. exposure to asthma triggers and adequate use of prescribed therapy. Control can also be influenced by how the healthcare system recognises and responds to patients who receive suboptimal therapy 5.

Many studies suggest that, on average, asthma patients do not use controller medicines optimally and that the resulting undertreatment puts the patient at risk of adverse outcomes, including asthma exacerbations, unscheduled visits to the consulting room, emergency room (ER) contacts and hospitalisations. A recent study identified additional risks factors for visits to the ER by asthma patients: absence of predetermined crisis plan, previous visits to ER facilities, and inadequate use of prophylactic medicines during a flare­up of an exacerbation 6. Poor compliance with controller medicines has been identified as a major determinant of hospitalisation due to asthma 7. Drug­utilisation studies have shown that medical resource utilisation (MRU) is increased three­fold among high users of inhaled β‐agonists. Furthermore, among these patients, hospital costs appear to be determined by disease severity 8. In their study, Lanes et al. 9 found that 8% of asthma patients had either a hospital admission or an ER visit during a 12­month study period; their hospital costs accounted for 25% of the total costs of asthma care.

While studies confirm that a minority of patients use the majority of medical resources for asthma, the relationship between the use of medical resources and either control or severity needs clarification 10. Also, it is unclear whether the relationship between control and MRU varies according to the degree of asthma severity. The present study examined MRU in adult patients with persistent asthma in France. The objectives were to provide descriptive information about direct cost of asthma care, and to identify variables related to the costs of MRU, with a specific emphasis on the relationship between cost and level of control and its variation according to asthma severity.

Materials and methods

Study timelines

Details have been published previously 3. Briefly, patients were evaluated over at least 18 months, of which the 12 months preceding the survey were considered as the study period and prior months were considered as the baseline period. Figure 1⇓ illustrates the study timelines.

• Download figure
• Open in new tab
• Download powerpoint

Fig. 1.—

The study timeline. ICS: inhaled corticosteroids.

Results

Descriptive cost analysis

Specific conditional medical resource utilisation costs

The distributions of specific MRU costs are displayed in table 3⇓.

View this table:

• View inline
• View popup

Table 3—

()Distribution of conditional specific medical resource utilisation MRU costs

A majority of the 1,038 patients visited their GP and received prescriptions for anti­asthma medicines during the study period (table 3⇑). However, specific costs for these two resources accounted for only 17% and 33% of total MRU cost, respectively. By contrast, only 9% of patients were hospitalised but this resource made up 49% of global expenses (fig. 2⇓). Visits to the ER had little impact on total MRU cost.

• Download figure
• Open in new tab
• Download powerpoint

Fig. 2.—

( )□%┘%%▪Specific expenses in total medical resource utilisation cost 760,863E in 1,038 patients. : hospitalisation 49; : asthma medications 33; : visits to general practitioner 17; : visits to emergency room.

Total medical resource utilisation costs

Median cost was 278.0 E and 25th and 75th percentiles were 133.4 E and 587.1 E, respectively. Total MRU costs ranged from 0–51,674 E, with an asymmetric distribution (fig. 3⇓). A long distribution tail appeared beyond 1,200 E, and 97 patients had their costs concentrated beyond 2,000 E. Based on recent symptoms, these 97 patients had a significantly lower level of control compared to the others (p<0.0001); they were also more likely to have access to free asthma care and to report asthma crisis during the past 12 months (p<0.001). For these 97 patients, the part of MRU due to hospitalisation exceeded 86% of the total cost (376,578 E/434,309 E). In 1,038 patients, 29 had a null value for total cost since they had no asthma­related MRU during the 12­month study. These patients did not differ from their 1,009 counterparts with non­null total MRU costs for any variable of the study except for comorbid conditions (p<0.0001): none of the null­cost patients had any comorbid diagnosis recorded.

• Download figure
• Open in new tab
• Download powerpoint

Fig. 3.—

Distribution of total medical resource utilisation costs in 1,038 patients.

Discussion

The level of asthma control as measured by recent symptoms is a major correlate of total MRU, including drug therapy, ambulatory care and hospital care in persistent asthma, increasing substantially with lesser levels of control. Poorly controlled asthma resulted in a significant 2.5­fold increase in MRU costs, compared to well­controlled disease. Asthma severity, as judged by the prescribed doses of inhaled corticosteroids in the prestudy period, was also associated with a significant increase in MRU costs independently of other cofactors. Finally, the following factors were also associated with increased cost of care: age, access to free asthma care, presence of comorbid conditions and asthma symptoms in the past year.

Both the level of control and degree of severity, as measured in this study, are correlates of MRU. Level of control and asthma severity were identified from distinct sources and at different points in time: prescription information for severity, i.e. the dose of inhaled corticosteroids prescribed by the family physician before the study period; and patient data for assessment of control, i.e. the patient's response to a specific questionnaire at the end of the study period. The level of control was assessed for a 2‐week period at the end of the study period. However, this level of control may reflect the patients' attitude towards asthma medications drug observance and avoidance of risk factors throughout the study period. In a recent survey, Vollmer et al. 13 found that a short­term control index was significantly related to healthcare utilisation in a consecutive 12­month period.

Asthma severity was assessed from average doses of prescribed inhaled corticosteroids during a baseline prestudy period (fig. 1⇑). The marker of severity in this study was correlated with access to free healthcare for asthma (p=0.0004), number of prescriptions of oral corticosteroids (p=0.01) and number of different classes of asthma medications prescribed during the 12­month study period (p<0.0001). Finally, the significant increase of MRU costs across degrees of severity is consistent with recent data from Serra­Batlles et al. 14. In that study, severity was based on the International Consensus Report on Diagnosis and Treatment for Asthma 15.

Control of asthma also had an important effect on costs, independently of severity. Poor control was associated with higher MRU in the preceding 12 months, suggesting that a significant part of the burden of asthma could be prevented with improved disease management. The comparison of MRU across levels of control within different degrees of severity is of interest. In all severity categories, costs increased significantly with decreasing levels of control. In each category, costs for “well­controlled” patients could be interpreted as indicative of the “minimal” costs of asthma care according to disease severity. A priori, such costs are nonpreventable, in contrast to the costs computed in groups with lesser levels of control.

Age correlation with cost is not surprising, since age is a known risk factor for resource consumption in asthma, as in other conditions 16. The significant relationship between comorbid conditions and cost was less expected in this rather young population (17–50 yrs) where asthma was the major morbidity. It suggests that conditions linked to asthma may have an impact on resource consumption 17. Concomitant psychiatric troubles have been shown to be associated with increased asthma morbidity, and they may contribute to increased costs 18. Having access to free asthma care also resulted in higher costs of MRU. These patients were older and had more comorbid conditions, but multivariate analyses suggested that access to free asthma care was associated with higher costs independent of these characteristics. This finding is in agreement with the purposes of access to free asthma care in France, provided to patients with more severe disease, independent of their socioeconomic status, after review of their medical history by Social Security experts.

Only crude comparisons can be made between the data presented here and information available for other countries. Barnes et al. 19 made a comparison of direct costs between countries; depending on the country and the study, hospital contacts comprised between 18–79% of direct costs, i.e. generally a lesser portion of the costs of MRU than in this study. Barnes et al. 19 found that improved control was associated with an increase in drug costs and more visits to the GP. It should be stressed that, as a result of the selection of patients with persistent asthma, the present data did not allow valid estimates of the total asthma burden in the French population, in contrast to data published by other investigators 19–21. Another effect of the selection of patients with persistent asthma may have been the relatively high incidence of hospital contacts. Nevertheless, this is also the result of efforts to collect data on this outcome directly from patients. The current authors have indeed demonstrated that care givers are not optimally informed of outcomes in asthma patients, and using family physician data may result in underestimates of the hospital­contacts incidence 22.

These points underline some limitations of using a GP prescription database in asthma outcomes research. However, important advantages should also be acknowledged, i.e. that such databases may be considered as a more valid tool to assess asthma severity than drug dispensing databases, since data are available on actual GP's prescriptions of inhaled corticosteroids. Those prescriptions may be considered as being a reflection of the care givers' instant perception of asthma control, at least in settings and at times where such prescriptions were issued with some reluctance 23. A selection criteria prescribed was at least three canisters of inhaled β‐agonists during the 6‐month period before the onset of the study. This could be considered as high β‐agonists consumption, but it was consistent with β‐agonists prescription patterns by GPs in France until recently.

This study had some other limitations. To compute medication costs, several assumptions were made, for example that patients took their prescriptions. Average costs were used to estimate the impact of admission to hospital for asthma, since there was no access to individual inpatient hospital­resource consumption data. Also, there may be recall bias in the responses to the survey questions, e.g. with some patients over­ or underestimating their rate of hospital admission. A selection bias could affect the results if there was a systematic, nonrandom, factor influencing the patient's decision to complete and return the questionnaire; 1,038 responders to questionnaires would then be different from 540 nonresponders. However, there were no significant differences between these two groups in demographic variables and asthma severity, though records of comorbid conditions were slightly higher among the 1,038 responders (p<0.04). Of 1,038 participants who completed the questionnaire, 101 did not answer specific questions for asthma control. This could represent another selection bias. However, patients with missing information on control did not differ from 937 others for costs or any variable in the study. If a selection bias cannot be excluded, its influence should be limited. Multivariate analyses were conducted in only 872 patients with non­null total MRU cost and valid data for all covariates. Except for comorbid conditions, these 872 subjects did not differ from their 166 counterparts for any other studied variables (data not reported). Furthermore, all multivariate results were consistent with univariate analyses.

In the final linear model, global R² did not exceed 0.17. Only a limited number of correlates for costs were identified. For example, the authors had no information on socioeconomic status, on education level, or on the attitude of the patients 24. However, a gradient of resource consumption was identified according to increasing severity or decreasing control, and this provided support to the assessment of these two diseases characteristics, and their relationship to resource consumption.

In summary, the results suggest that the major part of the cost burden of asthma is a consequence of both poor control and greater severity, especially for major outcomes, such as hospital admissions. Improvement in asthma control through improved disease management could potentially result in significant savings, in patient morbidity and costs to society 25. The findings also confirm that information obtained directly from patients is a useful addition to database information 3. The linkage of medical records to a specific patient survey may help to understand the complex relationship between severity and control in asthma, and to identify preferred areas of interventions to relieve the burden of asthma.