The Impact of Diagnosed and Undiagnosed Current Asthma in the General Adult Population

Background: Restrictive definitions of current asthma are used in epidemiological studies to achieve a highly specific classification of subjects. However, undiagnosed asthmatics should be taken into account to correctly evaluate the impact of the disease in the general population. Methods: In an Italian multi-centre cross-sectional survey carried out in 1998-2000, 18,647 responders (20-44 years old) to a screening questionnaire were classified as having physician-diagnosed current asthma or current respiratory symptoms. Similarities in the risk factor profile and in the socioeconomic burden were considered suggestive of undiagnosed current asthma. Results: In Italy, the prevalence of physician-diagnosed current asthma was 4.9% (95% CI 4.4-5.4), while that of 'asthma attacks and/or use of anti-asthmatic drugs in the past 12 months without a diagnosis of asthma' (ADWD) was 1.5% (95% CI 1.3-1.7). Allergic rhinitis was highly associated with diagnosed current asthma [relative risk ratio (RRR) 12.48; 95% CI 9.12-17.07; reference category: neither asthma during lifetime nor current respiratory symptoms] and with ADWD (RRR 8.42; 95% CI 6.33-11.19). Chronic cough/phlegm was homogeneously associated with all the respiratory conditions, and the strongest relationship was with ADWD (RRR 7.79; 95% CI 4.95-12.25). Subjects with ADWD and diagnosed current asthmatics were characterised by high and homogeneous percentages of individuals who reported productivity losses (19.0 and 15.1%) and hospitalisations (9.2 and 6.2%) because of respiratory problems in the past year. Conclusions: The impact of current asthma seems to be largely underestimated among Italian adults, since the individuals with ADWD may be undiagnosed current asthmatics.