Asthma is now a disease affecting 5% to 6% of the population or over 15 million people in the United States alone.<sup>19 Goldberg, Bruce J., Kaplan M.S. Non-asthmatic respiratory symptomatology Curr Opin Pulmon Med 2000 ;  6 : 26-30  [cross-ref]

Cliccare qui per andare alla sezione Riferimenti</sup> Although most asthma patients can be diagnosed and managed with standard measures, some patients can be classified as difficult to control even on high doses of inhaled corticosteroid medications.<sup>2 Barnes P.J., Woolcock A.J. Difficult asthma Euro Resp J 1998 ;  12 : 1209-1218  [cross-ref]

Cliccare qui per andare alla sezione Riferimenti</sup> An important reason for the difficulty in controlling asthma in certain individuals is the presence of concomitant diseases. These concomitant conditions can complicate diagnosis and management because of problems such as interactions between medications used for each disease, therapy for one condition complicating the other, and other problems encountered in patients with multiple diseases.<sup>29 Middleton E., Reed C.E., Ellis E.F. , e al.  St. Louis: Mosby (1998).  460-462 909–910.

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