Autoantibodies in patients with chronic bronchitis.

Antinuclear antibody (ANA) was found in low titre in 28% of a group of 50 patients with chronic bronchitis by MRC criteria and defined as "severe", that is having at least six infective episodes a year, a vital capacity of less than 70% of predicted and less than 30% reversibility of their airways obstruction after inhalation of isoprenaline. By contrast ANA was found in only 4% of age and sex matched non-bronchitic controls and in none of 28 patients with "less severe" chronic bronchitis in whom these three criteria of severity were not fulfilled. The presence of antinuclear antibody was unrelated to the duration of the disease, sputum volume or the presence of purulent sputum at the time of the study. Neither was it related to blood eosinophilia, respiratory function, smoking or the presence of bacterial precipitins in the patient's serum. These findings are important because they suggest that incidental chronic bronchitis, unless it is extremely severe, is unlikely to contribute substantially to the prevalence of antinuclear antibody found in certain other lung diseases. There was no significant increase in smooth muscle or "reticulin" antibodies in this series of patients.