[Clinical study on bronchial hyperresponsiveness and development of bronchial asthma in patients with persistent cough].

The purpose of this study was to ascertain whether in patients with persistent cough the presence of bronchial hyperresponsiveness (BH) and development of asthma could be speculated based on clinical data. Only patients who met strict criteria excluding exogenous factors that influence BH, especially smoking or respiratory infection, were included in this study. The study group included 15 males and 50 females aged 18 to 62 years (mean +/- S.D. of 44 +/- 12 years) whose physical findings, chest X-rays, spirometry results and peripheral leukocyte counts were within normal limits. Duration of cough was at least one month. The patients had no history of wheezing, dyspnea or previous bronchodilator therapy. None of them had ever been smokers. In addition, there was no history of upper respiratory tract infection in the preceding month. BH was assessed by "Astograph" using methacholine. Cmin and Dmir or SGrs/Grs cont. were measured as the indexes of bronchial sensitivity or reactivity respectively. A methacholine Cmin of 3, 125 micrograms/ml or less was taken as a positive indication of BH. The evaluated clinical data were age, pulmonary function (spirogram or flow volume curve), atopic factors (serum total IgE and family or personal history of atopic diseases), peripheral eosinophil count, bronchial sensitivity or reactivity, and clinical features of cough (induction by exercise or cold air and nocturnal worsening). The results were as follows. (1) Twenty-nine (45%) of 65 patients were BH-positive (BH-positive group). (2) There was no significant difference in age, %FVC, IgE, and family or personal history of atopic diseases between the BH-positive and negative group. However, the BH-positive group had significantly lower FEV1.0%, %FEV1.0, PEFR, (p less than 0.05) and V25/H (p less than 0.01) and a higher peripheral eosinophil count (p less than 0.05) than the BH-negative group. (3) Seventeen (85%) of 20 BH-positive patients prescribed bronchodilators (beta 2 agonist/theophylline) responded to therapy within a month. (4) Seven (29%) of 24 BH-positive patients available for 2 years follow-up developed clinical asthma. (5) There was no significant difference in %FVC, FEV1.0%, V25/H and peripheral eosinophil count between the patients who developed asthma (Group A) and those who did not (Group N-A). However, The patients in Group A were older than those in Group N-A.(ABSTRACT TRUNCATED AT 400 WORDS)