Active detection of chronic obstructive pulmonary disease and asthma in the general population - Results and economic consequences of the DIMCA program

The aim of this prospective study was to detect subjects In the general pop ulation with objective signs of chronic obstructive pulmonary disease (COPD ) or asthma at an early stage. This was done by means of a two-stage protoc ol involving screening and a subsequent 2-yr monitoring of all subjects wit h positive results of screening, The study was done in 10 general practices located in the eastern part of the Netherlands. A random sample was taken from the general population aged 25 to 70 yr. All known COPD and asthma pat ients were excluded. A total of 1,749 subjects met the inclusion criteria: 1,155 subjects (66%) agreed to participate in the screening stage of the st udy. A total of 604 subjects (52.3%) showed symptoms or objective signs of COPD or asthma during the screening and were considered "positive." Of thos e with positive screening results, 384 subjects (64%) agreed to participate in the second, 2-yr monitoring stage of the study. The costs involved in d etection were calculated for three different scenarios, as follows: (I) The detection of subjects with persistently decreased lung function or an incr eased level of bronchial hyperresponsiveness (BHR) during 6 mo of monitorin g; (2) Scenario 1 plus the detection of subjects with a rapid decline in lu ng function with signs of BHR during 12 mo of monitoring; (3) Scenario 2 pl us the detection of subjects with a moderate increase in the decline in lun g function or signs of BHR during 24 ma of monitoring. The costs of lung fu nction assessments, organization, transportation, and patient time were inc luded. The costs were converted to United States dollars on the basis of pu rchasing power (1 United States dollar = 2.08 Netherlands guilders). During the second stage, 252 subjects were defected with objective signs of COPD or asthma at an early stage. Smoking status as a screening criterion was ne ither sensitive nor specific. Because there was no evidence of biased recru itment or selection during the program, the proportions of subjects found t o have objective signs of COPD or asthma at an early stage could be extrapo lated to the general population. Of the general population, 7.7% showed per sistently reduced lung function or increased BHR. Another 12.5% of the gene ral population showed a rapid decline in lung function (> 80 ml/yr) in comb ination with signs of BHR, and a further 19.4% of the general population sh owed mild objective signs of COPD or asthma. The average costs per detected case varied from US$953 (Scenario 1) to US$469 (Scenario 3). In conclusion , detection of COPD or asthma at an early stage by means of a two-stage pro tocol was feasible at relatively little expense in comparison with other ma ss screening programs. Persistently decreased lung function or a rapid decl ine in lung function (Scenario 2) was observed in approximately 20% of the general adult population.