Can endobronchial biopsy analysis be recommended to discriminate between asthma and COPD in routine practice?

Background: International guidelines stress the importance of accurately discriminating between asthma and chronic obstructive pulmonary disease ( COPD). Although characteristic pathological features have been described for both conditions, their discriminatory power has never been systematically assessed. Methods: Endobronchial biopsy (EBB) specimens from patients with a clear clinical diagnosis of asthma and COPD (50 per group) were examined by three pathologists in a double blind manner. They were asked to propose a pathological diagnosis of either asthma or COPD and to analyse qualitatively the most frequent abnormalities reported in the literature. Results: The sensitivity and specificity of EBB ranged from 36% to 48% and from 56% to 79%, respectively. Eosinophils strongly biased the pathological diagnoses in favour of asthma, whereas their estimated prevalence was similar (11-37% in asthma and 13-41% in COPD). Metaplasia (11-39% in COPD, 1-18% in asthma) and epithelial inflammation (28-61% in COPD, 11-38% in asthma) tended to be specific to COPD, whereas epithelial desquamation (80-98% in asthma, 61-88% in COPD) and basement membrane thickening (71-94% in asthma, 53-88% in COPD) tended to be associated with asthma. There was acceptable intra- and inter-observer agreement only for metaplasia and epithelial eosinophils. Conclusions: Specific histopathological features of asthma and COPD probably exist, but current routine analysis procedures to assess EBB specimens are not sufficiently discriminatory. This might be rectified by improving pathological definitions.