Clinical applications of immunoglobulin G against different individual <i>Aspergillus</i> species for the diagnosis of chronic pulmonary aspergillosis among at-risk populations

<i>Aspergillus fumigatus</i>-specific IgG is often used as a diagnostic test for chronic pulmonary aspergillosis (CPA), but few studies have evaluated the performance and serology of IgGs from species other than <i>A. fumigatus</i>. In this study, we evaluated the serology and performance of different <i>Aspergillus</i> species-specific IgG antibodies in patients with CPA and at-risk populations and whether different <i>Aspergillus</i> species-specific IgGs could be of clinical utility and aid in the diagnosis of CPA caused by all <i>Aspergillus species</i>. A total of 187 participants were included between 2020 and 2022 (12 with CPA, 75 with old tuberculosis [TB], 45 with active TB and 55 with bronchiectasis). We measured the serum <i>Aspergillus fumigatus, flavus, terreus</i>, <i>niger</i>-specific, and mixed <i>Aspergillus</i> IgG levels (Phadia ImmunoCap). The correlation was the strongest between <i>A. fumigatus</i> and <i>A. niger</i> (Spearman’s rank: 0.940), followed by <i>A. niger</i> and <i>A. flavus</i> (Spearman’s rank: 0.915). <i>A. terreus</i>-specific IgG was less strongly correlated with the other three <i>Aspergillus</i> species-specific IgG (Spearman’s rank: 0.828–0.849). <i>A. flavus</i> (4 of 6, 67%) was the dominant species. Using the at-least-one-positive approach, the highest performance was obtained when <i>A. fumigatus</i> and <i>A. flavus</i> IgGs were used (sensitivity, 0.75; specificity, 0.84). Significant cross-reactivity exists among different <i>Aspergillus-</i>species IgGs although the correlation may be less significant for <i>A. terreus</i>. In addition to the commonly used <i>A. fumigatus</i> IgG test, IgGs specific to local prevalent <i>Aspergillus</i> species may provide additional clinical utility.