Bronchial hyperresponsiveness in asthmatic adults - A long-term correlation study

Background: Bronchial hyperresponsiveness (BHR), is a risk factor for asthma. It is a state in which excessive narrowing of the airways occurs in response to varying stimuli. BHR seems to be due to the interaction of multiple factors and its relation to asthma is complex. Asthma without BHR is unusual. Indeed, patients who show a higher degree of symptoms have higher levels of BHR. To date no study has investigated the correlation between BHR in mild persistent asthmatic adults and a long-term therapy of five years. The aim of this study is to evaluate (i) the role of BHR in the clinical evaluation of asthma, (ii) the correlation between BHR and therapy in asthma. Methods: Seventy patients (were recruited 34 men, age 21-55 years) suffering from: (a) mild seasonal allergic asthma (17/70), (b) mild perennial allergic asthma (34/70) and (c) mild allergic asthma (19/70). 14 patients from group (a) and 28 patients from group (b) were treated with inhaled β2-agonists, beclomethasone, disodium-cromoglycate and immunotherapy. 14 patients from group (c) underwent the same treatment regimen without immunotherapy. All patients were evaluated with a metacholine challenge test. The BHR (PD20 FEV1) was calculated at baseline and after a two-year symptom free period. Fifteen pts were followed-up for five years with an evaluation every year. All other patients did not receive any treatment. The results (expressed as mean ± SE) were evaluated. Results: Fourteen pts and three pts from group (a) showed a mean BHR value of 984 ± 3.66 and 674 ± 2.06; 343 ± 7.60 and 208 ± 7.70 respectively. The results were not statistically significant Twenty-eight and six pts from group (b) showed mean values of 685 ± 1.45 and 1405 ± 5.65; 856 ± 7.09 and 435 ± 2.20 with apparent improvement for the former. Five pts and fourteen pts from group (c) showed mean value of 2682 ± 7.85 and 2099 ± 6.82; 816 ± 2.53 and 877 ± 4.78 respectively. As for the 5-yr follow up ten pts and five pts from group (b) showed mean values of 705 ± 1.6 and 861 ± 7.15; 911 ± 7.3 and 457 ± 2.3 respectively. Conclusions: Although the clinical picture improved with therapy, BHR was not significantly affected in any patient group, at two and five years of follow-up. Furthermore, no correlation was found between the clinical picture and PD20 FEV1 values. BHR seems to result from the interaction of multiple factors that are worth further investigating. BHR cannot be considered a marker of disease activity in asthma and therefore is not a useful tool for guiding asthma therapy.