PURPOSE: There is neither uniform consensus on the number of criteria needed for diagnosis nor the specific cut-off values for the various parameters employed in diagnosis of ABPA. Traditionally an AEC of >1000 cells/μL is considered an important criteria for diagnosis of ABPA. This study attempts to delineate the significance of peripheral blood eosinophil counts in the diagnosis of ABPA, and its relationship with lung function, immunological and radiological parameters.
METHODS: This is a retrospective analysis of previously published data of 209 glucocorticoid naive patients of ABPA(Chest 2006;130:442-8; Chest2007;132:1183-90; Respir Med 2010;104:204-10; PLoS One 2010; 5:e15346). Based on AEC, patients were classified into three categories: <500; 500-1000; and >1000 cells/μL, and their relationship with spirometric, immunological and radiological characteristics was assessed.
RESULTS: There were 108 males and 101 females with a mean (SD) age of 34.1 (12.5) years. The median (IQR) AEC at diagnosis was 850 (510-1541) cells/μL, and 60% of the patients had an AEC <1000 cells/μL. There was no relationship of AEC with lung function on spirometry and other immunological parameters. The values of AEC and IgE levels (total and Aspergillus specific) were converted to their corresponding logarithmic values, and a linear regression was performed to assess significance of their relationship. The linear regression yielded an r2 value of 0.018 for total IgE and 0.001 for Aspergillus specific IgE. The median AEC were higher in patients with bronchiectasis (986 vs. 620, p=0.001)and high-attenuation mucus (1200 vs. 800, p=0.001)on high resolution CT of the lungs.
CONCLUSIONS: AEC in peripheral blood has limited utility in the diagnosis of ABPA. There is no relationship of AEC with lung function and other immunological parameters. However, higher AEC in patients with central bronchiectasis and high-attenuation mucus points towards possible role of eosinophils as an important inflammatory mediator in ABPA
CLINICAL IMPLICATIONS: Though of limited use in making a diagnosis of ABPA, high AEC is associated with a more severe form of disease
DISCLOSURE: The following authors have nothing to disclose: Dheeraj Gupta, Ritesh Agarwal, Neelam Varma, Mandeep Garg, Biman Saikia, Arunaloke Chakarbarti
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