INTRASUBJECT VARIABILITY IN AIRWAY INFLAMMATION SAMPLED BY BRONCHOALVEOLAR LAVAGE IN STABLE ASTHMATICS

Despite the increasing complexity of bronchoalveolar lavage (BAL) stud ies in asthmatics there are few published data concerning the variabil ity of inflammatory parameters measured using this technique. We studi ed the intrasubject variability of cellular and solute parameters in 2 0 clinically stable, symptomatic, mild-to-moderate asthmatics, in repe at 180 mt BAL procedures performed 1 month apart, During the study, th ere was no change in disease activity or medication. Mean (SD) forced expiratory volume in one second (FEV1) was 3.2 (1.09) L at the first B AL and 3.05 (0.98) L at the second, The geometric mean dose of methach oline provoking a 20% decrease in FEV1 (PD20) was 23 mu g (range 2-1,1 70 mu g) at the first BAL and 28 mu g (range 2-440 mu g) at the second , There was considerable variability in the BAL cellular and solute pa rameters measured over the two procedures, Estimates of power calculat ed for subsequent studies involving this type of subject group were ma de from the observed variability. Sample sizes of less than 15 mean th at differences have to be targe in order to be detected in repeat BAL samples, However, there is little improvement in the power of BAL stud ies for sample sizes greater than 20, indicating that there is little gain in recruiting more than this number of subjects. Thus, our study indicates that although studies of the pathophysiology underlying asth ma using BAL require considerable commitment, they are practicable.