Comparison of ﬁxed-dose combinations for asthma 1873 Statistical analysis Logistic regression was used to estimate the associa- tion between treatment group and treatment success, adjusting for patient characteristics. Treatment suc- cess was modelled as a dichotomic variable, grouping the categories ‘partial success’ and ‘no success’ together. Potential covariates included disease sever- ity according to treatment history, age and insurance status, and centre characteristics according to the physician and the specialty of the lead physician. Covariates that were not statistically signiﬁcant at the 5% level were removed. Renewal rates of ICS ⁄ LABA prescriptions were assessed as a measure of treatment persistence. Generalised linear models were used to estimate the effect of treatment on severe exacerba- tions, resource use and costs, adjusting for patient and physician characteristics. The choice of statistical distribution was based on goodness-of-ﬁt statistics, which lead to the application of lognormal and gamma distributions, depending on the type of resource or cost modelled. Results Patients Among the 2438 patients who met the study inclu- sion criteria, 1456 were treated with budesonide ⁄ formoterol (administered via Turbuhaler) and 982 were treated with salmeterol ⁄ ﬂuticasone (adminis- tered via Diskus in the majority of patients). These patients represented 7.1% and 4.8% of the database respectively (Figure 1). The majority of exclusions were due to patients not fulﬁlling 24 months of fol- low-up or having no history of asthma. Patient char- acteristics are summarised in Table 3. The mean age was approximately 48 years in both groups and there were no signiﬁcant differences between groups in markers of disease severity in the pre-index year, based on prescriptions of asthma medication, refer- rals (p = 0.2829) or hospitalisations (p = 0.7764). SABA prescriptions in the pre-index year were recorded in 41.2% and 39.8% of patients in the salmeterol ⁄ ﬂuticasone and budesonide ⁄ formoterol groups, respectively, at an average of approximately 1.8 inhalations per day [dry power inhaler (DPI) equivalent]. There was no statistically signiﬁcant difference in reported comorbidities between groups (rhinitis, p = 0.0867 and gastro-oesophageal reﬂux disease, p = 0.9764). In both groups, the majority of patients were fol- lowed at a general practitioner (GP)-lead clinic and the minority were followed at a specialist-lead prac- tice. However, comparison of the two groups showed a higher proportion of patients at GP-lead clinics in Table 2 Unit costs Type of cost Physician Patient age 12–59 years > 60 years Allergologist Pneumologist Hospitalisation associated with asthma G-DRG associated with asthma diagnosis Bronchitis and bronchial asthma, > 55 years old or with heavy complications (1619 cases) Bronchitis and bronchial asthma, age 6–59 years old and without heavy complication (2118 cases) Diseases ⁄ disturbances of respiratory organs, with artiﬁcial respiration > 24 h, without complication (6 cases) Unit Routine visit Asthma-related visit Routine visit Asthma-related visit Referral Referral Hospital stay Hospital stay (6.8 days) Hospital stay (4.0 days) Hospital stay (10.2 days) Cost, € 6.75* 29.50* 10.75* 33.50* 87.75* 57.20* 1607.35 2012.50§ 1378.46§ 5651.31§ *Unit costs obtained from EBM schedules, assuming a unit cost of €0.05 for each EBM point. It was assumed that two spirographies and one body plethysmography were conducted for all referrals. An estimated average cost calculated from the three G-DRG associ- ated with a possible main diagnosis of asthma or acute exacerbation. This weighted average cost was calculated based on the number of cases associated with one asthma diagnosis and a co-payment of €10 per hospital day was applied. §Unit costs obtained from G-DRG (http://www.g-drg.de/). G-DRG, German reﬁned diagnosis-related groups; EBM, Einheitbewertungsmaßstab. ª 2008 Ingenix Pharmaceutical Services (UK) Ltd. Journal compilation ª 2008 Blackwell Publishing Ltd Int J Clin Pract, December 2008, 62, 12, 1870–1879