Fungal culture and sensitisation in asthma, cystic fibrosis and chronic obstructive pulmonary disorder: what does it tell us?
[allergic bronchopulmonary aspergillosis]
Collectively asthma, chronic obstructive pulmonary disorder (COPD) and cystic fibrosis (CF) are very common, important causes of disease and ill health. Filamentous fungal colonisation of the airways can occur in all three disease groups, although the clinical relevance is unclear. Allergic bronchopulmonary aspergillosis (ABPA) is a well-recognised severe complication of airway colonisation associated primarily with Aspergillus fumigatus. Fungal colonisation may have a deleterious effect without fulfilling all the diagnostic criteria of ABPA; however, a lack of standardisation in processing respiratory samples hampers comparisons. Whilst mycology laboratory accreditation programs are common, most countries have no national standard guidelines for processing respiratory samples. Fungal recovery from sputum in CF, asthma and COPD can be around 40, 54 and 49 %, respectively. Isolation of fungi from sputum has been associated with reduced lung function in asthma and CF, although no such associations have been found in COPD. It is unclear whether fungal colonisation contributes to lower lung function or is a marker of more severe lung disease and aggressive therapy. Fungal sensitisation may contribute to the persistence of active respiratory symptoms; however, the exact prevalence is unclear. Sensitisation to A. fumigatus has been associated with reduced lung function in asthma, COPD and CF. It has suggested that both skin prick tests and specific IgE measurement by the ImmunoCAP system should be used in diagnoses of allergy, due to discordance in test results; however, there is currently no widely adopted consensus as to which fungi to test for.