Airways hyperresponsiveness, bronchodilator response, allergy and smoking predict improvement in FEV1 during long-term inhaled corticosteroid treatment. Dutch CNSLD Study Group.

Although most patients with obstructive airways disease show some amelioration with long-term inhaled corticosteroid therapy, the extent of improvement may vary considerably between patients. Patients with mild to moderately severe obstructive airways disease (asthma and COPD) were selected if provocative concentration producing a 20% fall in forced expiratory volume in one second (PC20) < or = 8 mg.ml-1, and forced expiratory volume in one second (FEV1) < 95% confidence intervals (CI) of predicted normal. The independent influences of baseline PC20FEV1, inspiratory vital capacity (IVC), bronchodilator response, smoking habits, and allergy both on the "immediate" (within 3 months) response in FEV1 and the change in long-term (from 3 months onwards) slope of FEV1 with inhaled corticosteroids were analysed. Patients had a larger "immediate" improvement in their FEV1 with inhaled corticosteroids with each doubling doses lower PC20, with each ten-fold higher immunoglobulin E (IgE), and if they did not smoke. Total IgE proved a better independent predictor of "immediate" response than specific IgE for house dust mite, skin tests, or blood eosinophils. A more favourable long-term slope of FEV1 was predicted by a larger baseline bronchodilator response, but not by smoking. In conclusion, PC20, total IgE, and smoking habits are independent predictors of immediate treatment response to inhaled corticosteroids. Bronchodilator response is the single independent predictor of changes in long-term slope of FEV1 with corticosteroid treatment.