Changes in peak expiratory flow indices as a proxy for changes in bronchial hyperresponsiveness

Guidelines for asthma management advocate home peak expiratory flow (PEF) m onitoring. It is commonly stated that PEF variability is a good prosy of br anchial hyperresponsiveness (BHR), a hallmark of asthma, However, this has hardly been tested longitudinally, as required to monitor asthma, This stud y assesses which PEF index correlates best with BHR longitudinally and whet her the correlation improves when correcting PEF values for the known nonli nearity of mini-Wright PEF meters, Every 6 months, for a period of 2 yrs. PEF diary cards were filled in and B HR to histamine was tested in 104 patients with BHR and reversible airways obstruction, who started treatment with bronchodilators with (n=33) or with out (n=71) inhaled corticosteroids, Within each subject, PEF indices and BH R were correlated longitudinally. The highest median correlation coefficients were obtained in the group of p atients using inhaled corticosteroids. The PEF indices providing the best c orrelation with BHR were: mean PEF bronchodirator response (rho=-0.50) and within-day variation (% mean or % maximum) (with postbronchodilator values, rho=-0.50; without postbronchodilator values, rho=-0.40). Using PEF data c orrected for the nonlinearity of the PEF meters did not result in higher co rrelation coefficients, Since current guidelines on asthma management recommend only bronchodilator s on demand, the most useful peak expiratory flow index far reflecting bron chial hyperresponsiveness longitudinally is mean within-day peak expiratory flow variation (% mean or % maximum) (without postbronchodilator values). Since the correlation coefficients are not very strong, the authors suggest that peak expiratory now measurements are not used as a prosy for bronchia l hyperresponsiveness longitudinally hut as a measurement in its own right. The use of corrections of peak expiratory flows far the nonlinearity of mi ni-Wright peak expiratory flow meters does not improve the correlation betw een peak expiratory flow and branchial hyperresponsiveness.