Diagnostic performance of Aspergillus-specific immunoglobulin G immunochromatographic and enzyme-linked immunosorbent assay testing in chronic pulmonary aspergillosis: comparative analysis across subtypes and influencing factors.

BACKGROUND

Elevated serum Aspergillus-specific immunoglobulin G (IgG) is a key diagnostic criterion for chronic pulmonary aspergillosis (CPA). This study evaluated the diagnostic performance of Aspergillus-specific IgG testing, comparing rapid immunochromatographic point-of-care test (ICT-POCT) with enzyme-linked immunosorbent assay (ELISA) for CPA and its subtypes, while identifying factors influencing test accuracy.

METHODS

We recruited 112 CPA patients and 61 non-CPA controls with pulmonary diseases from The First Affiliated Hospital of Guangzhou Medical University between December 2021 and November 2022. CPA diagnosis followed composite clinical, radiological, and microbiological criteria. Serum Aspergillus-specific antibodies were analyzed using quantitative ELISA (IgG) and ICT [IgG/immunoglobulin M (IgM)]. Bronchoalveolar lavage (BAL) Aspergillus galactomannan (GM) was tested where available. Sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV) were calculated.

RESULTS

90% of CPA patients had elevated Aspergillus-specific IgG antibodies by ImmunoCAP. ICT assay demonstrated superior overall diagnostic performance (sensitivity: 88.4%; specificity: 95.1%) vs. ELISA [58.9% sensitivity, 82.0% specificity at 80 arbitrary units per milliliter (AU/mL) cut-off]. Combined testing achieved peak specificity (98.4%) but reduced sensitivity vs. individual tests. Among patients with a history of antifungal treatment, the sensitivity of ICT assay varied by subtypes: 78.6% for chronic cavitary pulmonary aspergillosis (CCPA), 57.1% for chronic fibrosing pulmonary aspergillosis (CFPA), 66.7% for simple aspergilloma (SA), 66.7% for subacute invasive aspergillosis (SAIA), and 50% for Aspergillus nodule(s) (AN). In addition, the sensitivity of the ICT assay differed in comorbidities: 76.5% in patients with chronic obstructive pulmonary disease (COPD), 97.3% in patients with bronchiectasis, and 96.7% in patients with cavitary pulmonary tuberculosis. Notably, prior antifungal and steroid therapy decreased the performance of both assays.

CONCLUSIONS

The Aspergillus-specific IgG ICT assay shows significant diagnostic value for CPA, particularly in untreated patients and CCPA subtype. Its high specificity and rapid format position it as a valuable point-of-care tool for prompt CPA diagnosis in resource-limited settings.