[Differential diagnosis of chronic obstructive lung disease, A statistical analysis of the discriminating power of various lung function tests (author's transl)].

Among 65 patients admitted to the hospital for chronic obstructive lung disease, the following pulmonary tests were systematically performed : spirometric vital capacity and total lung capacity, FEV1, functional residual capacity and total lung capacity measured by body plethysmography, airway resistance and specific conductance, CO diffusion capacity measured by single-breath test, N2 clearance by single breath oxygen dilution, and blood gases. The patients were divided into bronchitics, emphysematous and broncho-emphysematous, according to the clinical and radiological Nash's score, and to another personal score derived from the former. The simple and multiple correlations between the clinico-radiological score and the functional results are low. The clustering analysis groups the 65 patients into four clouds of points, around two principal axes : the volume axis and the overinflation axis. This study indicates that the most suggestive results for emphysema diagnosis are increased FRC and TLC and low Tlco/V'a. The clinical score is not dominant for the clustering of the patients into the dynamic clouds. Beneath the bronchitic, the broncho-emphysematous and the emphysematous groups, the clustering analysis individualizes a fourth group of cases characterized by chronic asthma, and which were not isolated by Nash's score.