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Background Allergic Bronchopulmonary Aspergillosis (ABPA), can seriously impact respiratory function in Cystic Fibrosis (CF). Diagnostic criteria for ABPA are variable in different studies. We aimed to determine the sensitivity and specificity of different markers in diagnosing ABPA. We hypothesised that a four-fold rise in total IgE levels to a value above 500 kU/L is more sensitive and specific than a rise in Aspergillus fumigatus (AF) sIgE to >5.7 kU/L.
Methods 312 paediatric CF patients were included, of whom 20 had been treated for ABPA in the last 5 years. We recorded age, CF genotype, pancreatic sufficiency status, percentage predicted FEV1, lung clearance index, serum eosinophils, total IgE, AF sIgE and AF IgG for the most recent and penultimate annual assessments (for non-ABPA patients) and for the time of diagnosis and the preceding annual assessment (for ABPA patients). Both absolute values and change over time in ABPA markers were analysed.
Results A four-fold rise in total IgE to a level >500 kU/L between the annual assessment preceding ABPA diagnosis and the time of diagnosis was found to be 100% specific, but only 27.8% sensitive. Rise in AF sIgE from below to above 5.7 kU/L at time of ABPA diagnosis was 99% specific and 33.3% sensitive. Absolute values of total IgE >500 kU/L and AF sIgE >5.7 kU/L gave 75% sensitivity.
Conclusions A four-fold rise in total IgE to >500 kU/L or AF sIgE rise to >5.7 kU/L are highly and equally specific for ABPA. High total IgE >500 kU/L, even without a four-fold rise, may also indicate ABPA.
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