Comparison of spirometric changes in the response to bronchodilators of patients with asthma or chronic obstructive pulmonary disease.
OBJECTIVE
Making the differential diagnosis between asthma and chronic obstructive pulmonary disease (COPD) based on the response to inhaled bronchodilators by means of spirometry is controversial. The objective of this study was to identify the most useful spirometric variables in order to distinguish between asthma and COPD.


METHODS
Retrospective study conducted from April of 2004 to January of 2006, comparing the spirometric parameters of 103 nonsmoking patients with asthma to those of 108 patients with COPD who were smokers for more than 10 pack-years. All of the patients included in the study were older than 40 and presented stable disease at the time of the test.


RESULTS
Initial forced expiratory volume in one second (FEV1) was the same in the two groups (pre-bronchodilator VEF1 = 51%). However, patients with COPD were older (66 +/- 9 years vs. 59 +/- 11 years, p < 0.001) and more frequently male (73 vs. 27%, p < 0,001).After the use of the bronchodilator, the median absolute difference in FEV1 was 0.25 L (range, -0.09 to 1.13 L) in patients with asthma and 0.09 L (range, -0.1 to 0.73 L) in those with COPD (p < 0.001). The highest sensitivity (55%), specificity (91%) and likelihood ratio (6.1) for asthma diagnosis was obtained when the percentage increase in postbronchodilator FEV1 in relation to the predicted FEV1 (Delta%prevVEF1) was equal to or greater than 10%. Isolated significant increases in forced vital capacity were more common in patients with COPD.


CONCLUSIONS
In patients over the age of 40 and presenting obstructive lung disease, a Delta%prevVEF1 >or= 10% is the best spirometric parameter to distinguish asthma from COPD.
Silvestri
Isabella Correia
IC
Hospital do Servidor Público Estadual de São Paulo, São Paulo, Brasil.
Pereira
Carlos Alberto de Castro
CA
Rodrigues
Sílvia Carla Sousa
SC
D000328:Adult; D001249:Asthma / Q000175:diagnosis* / Q000503:physiopathology; D001944:Breath Tests; D001993:Bronchodilator Agents; D003937:Diagnosis, Differential; D005260:Female; D005541:Forced Expiratory Volume; D006801:Humans; D016013:Likelihood Functions; D008297:Male; D008875:Middle Aged; D029424:Pulmonary Disease, Chronic Obstructive / Q000175:diagnosis* / Q000503:physiopathology; D012189:Retrospective Studies; D012680:Sensitivity and Specificity; D017678:Sex Distribution; D012907:Smoking / Q000009:adverse effects / Q000503:physiopathology*; D013147:Spirometry; D014797:Vital Capacity
D001993:Bronchodilator Agents