Role of <i>Aspergillus fumigatus</i>‐specific IgG in diagnosis and monitoring treatment response in allergic bronchopulmonary aspergillosis

Abstract

Few studies have evaluated the utility of Aspergillus fumigatus-specific IgG in allergic bronchopulmonary aspergillosis (ABPA). Herein, we evaluate the role of specific IgG in diagnosis and monitoring treatment response in ABPA. Forty-eight control subjects with A. fumigatus-associated asthma underwent A. fumigatus-specific IgG measurements at baseline, while specific IgG was assayed in 102 treatment-naïve subjects of ABPA at baseline, after eight weeks of glucocorticoid therapy, and during exacerbations. For determining the cut-off of A. fumigatus-specific IgG, we randomly classified two-thirds of the study subjects (cases and controls) as the derivation cohort, while the remaining one-thirds were labelled as the validation cohort. The best cut-off value of A. fumigatus-specific IgG in the derivation cohort was 26.9 mg_A /L (sensitivity: 88%; specificity: 100%). Using this limit, the sensitivity and specificity of A. fumigatus-specific IgG in diagnosis of ABPA was 89% and 100%, respectively, in the validation cohort. In contrast, the sensitivity of Aspergillus precipitins was only 27.4%. Following treatment, the A. fumigatus-specific IgG increased in 38 (37.2%) subjects, while it decreased in three (23.1%) of the 13 subjects experiencing an exacerbation. The A. fumigatus-specific IgG was found to be an extremely useful test in the diagnosis and differential diagnosis of ABPA but is unreliable in monitoring treatment response in this disorder.