# How Should IgG Seroconversion to Aspergillus fumigatus be Interpreted in Children With Cystic Fibrosis

## TL;DR

The study shows that IgG seroconversion to Aspergillus fumigatus in children with cystic fibrosis is linked to worsened lung function and disease progression.

## Contribution

The study introduces a novel clinical interpretation of IgG seroconversion in pediatric cystic fibrosis patients.

## Key findings

- Children with A. fumigatus IgG seroconversion had lower lung function and more exacerbations.
- Higher IgE levels against A. fumigatus were observed in seroconverted children.
- CT scans showed more bronchiectasis and infiltrates in seroconverted children.

## Abstract

Cystic fibrosis (CF) is one of the most common autosomal recessive diseases in the world population. Allergic bronchopulmonary aspergillosis (ABPA) is a severe complication of CF, the diagnosis of which is based on symptoms and blood IgE levels. However, many techniques of specific IgG levels’ measures are used, whose clinical significance is still unclear. We evaluated the clinical evolution of CF in children who presented a first A. fumigatus IgG seroconversion.

Monocentric pediatric case‐control study led in Rouen, France. Every patient with a first A. fumigatus IgG seroconversion was paired with a seronegative patient. Clinical data, functional respiratory investigations, CT scan, and biologic data were collected a year before (Y
−1), at the time of IgG seroconversion (Y
0), and one year after (Y
+1).

Thirty‐six cases were paired with 36 controls. Median age was 8. Forced expiratory volume in 1 s (FEV1) and forced vital capacity (FVC) were significantly lower at Y
+1 (p = 0.025) and Y
0 (p = 0.027), respectively, and more pulmonary exacerbations were observed in the case population (p = 0.047). Higher levels of specific IgE against A. fumigatus were observed at Y
−1 (p = 0.001), Y
0 (p = 0.014), and Y
+1 (p = 0.04) in the case population. On the CT scan, bronchiectasis and pulmonary infiltrates were more frequent in the case population (p = 0.01 and p = 0.003, respectively).

We found that the first A. fumigatus IgG seroconversion was associated with changes in clinical, respiratory functional, biologic, and radiologic parameters in CF pediatric population. A. fumigatus IgG seroconversion is an important step in the evolution of CF. A systematic search for seroconversion is therefore essential to assess the measures to be taken.