Estimating severe asthma prevalence in austria using nationwide prescription data

Background: Expert statements suggest that severe asthma (SA) represents 5-10% of the total asthma population, although limited data support this estimate. SA is characterized by high-intensity treatment to maintain asthma control, which corresponds to a treatment of GINA steps 4 and 5 with a high-dose inhaled corticosteroids (HD-ICS) combination treatment. Objective: The aim of this study is to estimate the prevalence of SA based on the 2014 ERS/ATS criteria. Methods: All persons claiming at least one prescription for anti-obstructive drugs (ATC-R03) in 2011 or 2012 were extracted from administrative databases of the Main Association of Austrian Social Security Organisations, covering >98% (8,273,700) of the Austrian population. A total of 994,275 persons claimed 8,259,034 ATC-R03 prescriptions. Average daily ICS doses were calculated and patients receiving HD-ICS combination therapy classified as SA. Results: Based on treatment level, 2,239 persons qualified for the diagnosis of SA (prevalence: 0.027%). The mean age was 62±13 years and 44 % were women. Prevalence increased with age, while in children or adolescents, nearly no HD-ICS combination therapy was present. Based on the Austrian asthma prevalence (5.8%), our findings imply that only 0.47% of all asthmatics classifies for SA (2.7 pat. per 10,000 persons). Conclusion: These unexpected findings suggest that the prevalence of SA might be lower than estimated by expert opinion.