LACK OF CORRELATION BETWEEN BRONCHOCONSTRICTOR RESPONSE AND BRONCHODILATOR RESPONSE IN A POPULATION-BASED STUDY

Bronchodilator and bronchoconstrictor responsiveness have been conside red physiological opposites in patients with obstructive airways disea se, Provocation challenges have been replaced by bronchodilator tests in the assessment of cases of severe airways obstruction, The aim of t his study was to examine the relationship between bronchoconstrictor a nd bronchodilator responsiveness, and their supposed interchangeabilit y, in a general population, From the Vlagtwedde-Vlaardingen follow-up study, 101 adults were recruited (mean (so) age 55 (11) yrs, 67 males and 34 females, and 31 were smokers), All completed a questionnaire on airways symptoms, Bronchoconstrictor and bronchodilator responsivenes s were assessed with cumulative dose-response curves, using histamine and terbutaline, respectively. Thus, it was possible to relate histami ne sensitivity of the airways (the concentration of histamine, at whic h forced expiratory volume in one second (FEV1) falls by 10% (PC10)) t o the maximal bronchodilator response (Delta FEV1) and the sensitivity to the bronchodilator (cumulative dose of inhaled terbutaline at whic h FEV1 increases by 10% (RD10)). Subjects with a bronchoconstrictor re sponse (PC10 less than or equal to 16 mg.mL(-1); n=38) had more respir atory symptoms than those without (n=63) (40 versus 21%) and also lowe r baseline FEV1 values (90 versus 96% predicted), but had comparable b ronchodilator responsiveness, Subjects with a bronchodilator response (Delta FEV1 greater than or equal to 9% of the predicted value; n= 13) did not differ from those without (n=88) for all parameters, includin g symptoms, allergy and pulmonary function, In those with a bronchocon strictor response, there was a weak but significant correlation betwee n the PC10 and RD10 (rho= -0.32), but not between FC10 and Delta FEV1. This study suggests that bronchoconstrictor and bronchodilator respon siveness are not highly correlated, even in subjects with airways obst ruction, Symptoms were associated with the presence of a bronchoconstr ictor, but not a bronchodilator, response, We conclude that bronchocon strictor and bronchodilator responsiveness are two different phenotypi c markers that are not interchangeable in epidemiological studies.