Interest of immunoblotting with Aspergillus fumigatus western blot IgE assay for the differential diagnosis of IgE sensitisation and allergic broncho pulmonary aspergillosis

Raphaël Piarroux *1, Stéphane Ranque 2, Joana Vitte 2

Author address: 

1 Lyon, LDBIO Diagnostics, Lyon, France; 2 Aix-Marseille University, IRD, APHM, IHU-Méditerranée Infection, VITROME, Marseille, France

Abstract: 

Background: Allergic Broncho-Pulmonary Aspergillosis (ABPA) diagnostic is complex and based on a multi-criteria definition. One of the major criteria is the presence of specific immunoglobulin E (sIgE) to Aspergillus fumigatus (Af), but sIgE also reflects sensitization to Af. Discrimination between Af sensitization and ABPA is complex, and no diagnostic test allows a clear distinction between these two entities to date. We recently reported that a Western Blot detecting IgE antibodies specific for Af could separate those two entities. This work aimed to evaluate the LDBIO A. fumigatus WB IgE assay for differentiating ABPA from Af-sensitization.

Materials/methods: 229 sera (2014-2018 period, Marseille, France) with known sIgE reactivity (23 ABPA, 206 Af-sensitized) were assayed with the LDBIO A. fumigatus WB IgE. All had been previously assayed with ImmunoCap® for sIgE. We evaluated the ability of WB to detect Af sensitization and to discriminate between ABPA and Af-sensitized patients, relying on ImmunoCap® and clinical chart conclusions as a reference.

Results: Samples displayed 0 to 10 bands in the 10-37 kDa range. The 4 most frequent bands were considered as major bands (16, 18-20, 22 and 30 kDa) and the others as minor bands (10, 17, 33, 34, 36 and 37 kDa). A. fumigatus WB IgE positivity was defined by the presence of 2 major bands. This WB was thus positive in 23/23 ABPA and 124/206 Af sensitizations sera (64% sensitivity). WB positivity was strongly correlated to sIgE level; it was positive in 95% (98/103) of the sera with sIgE >1.5 kUa/l.

The ABPA WB IgE profile was defined by the presence of at least 2 major bands and 2 minor bands with 96% sensitivity (22/23) and 93% specificity (192/206) for ABPA diagnostic.

Conclusions: This study highlights the interest of the WB A. fumigatus IgE assay in the work-up of IgE responses to Af in asthmatics and cystic fibrosis patients: WB could discriminate ABPA from Af-sensitized patients with a sensitivity of 96% and a specificity of 93%. These encouraging results must now be reproduced in a multicentric evaluation.

Presenter email address: [email protected]

2020

abstract No: 

5493

Full conference title: 

European Congress of Clinical Microbiology and Infectious Diseases 2020
    • ECCMID 30th (2020)