PCR based bronchoscopic detection of common respiratory pathogens in chronic cough: a case control study

Bronchoscopic endobronchial biopsies and bronchoalveolar lavage cell counts were obtained from ten healthy volunteers and twenty treatment resistant chronic cough patients (10 selected for lavage lymphocytosis). A screen for known respiratory pathogens was performed on biopsy tissue. Chronic cough patients also underwent cough reflex sensitivity testing using citric acid.There was no significant difference in incidence of infection between healthy volunteers and chronic cough patients (p？=？0.115) or non-lymphocytic and lymphocytic groups (p？=？0.404). BAL cell percentages were not significantly different between healthy volunteers and chronic cough patients without lymphocytosis. Lymphocytic patients however had a significantly raised percentage of lymphocytes (p？<？0.01), neutrophils (p？<？0.05), eosinophils (p？<？0.05) and decreased macrophages (p？<？0.001) verses healthy volunteers. There was no significant difference in the cough reflex sensitivity between non-lymphocytic and lymphocytic patients (p？=？0.536).This study indicates latent infection in the lung is unlikely to play an important role in chronic cough, but a role for undetected or undetectable pathogens in either the lung or a distal site could not be ruled out.Current Controlled Trials ISRCTN62337037 & ISRCTN40147207Cough is a common reason for patients to seek medical attention [1]. It is well known that viral infection of the upper respiratory tract is the most common cause of acute cough [2] and an increase in cough reflex sensitivity has been demonstrated during upper respiratory tract infections (URTI) in healthy subjects, similar to that seen in patients with chronic cough [3,4]. Most respiratory infections which lead to cough are caused by viruses such as picornaviruses, coronaviruses, parainfluenza, influenza A and B, human metapneumovirus, respiratory syncytial viruses and adenoviruses. But they may also be caused by other pathogens such as human bocavirus or mycoplasma [5-8].About one third of ch