Improving Diagnostic Sensitivity of Chronic Pulmonary Aspergillosis Using Species-Specific IgG

Chronic pulmonary aspergillosis (CPA) is most commonly caused by Aspergillus fumigatus (AF-CPA). Serum A. fumigatus-IgG, a pivotal investigation for diagnosing CPA, misses 10%-15% of CPA cases. We aimed to determine whether measuring serum IgG against non-fumigatus Aspergillus species enhances the serodiagnosis of CPA.

We prospectively enrolled consecutive, treatment-naïve adults with CPA. The diagnosis of CPA was made using the ESCMID-ERS criteria. Serum IgG against Aspergillus fumigatus, Aspergillus flavus, Aspergillus niger and Aspergillus terreus (cut-off, 27 mgA/L) was measured by fluorescent enzyme immunoassay. Non-fumigatus-CPA (NF-CPA) was defined when non-fumigatus species-specific IgG titres exceeded A. fumigatus-IgG by ≥ 25%. The primary objective was to evaluate the incremental diagnostic yield of non-fumigatus species-specific IgG for identifying CPA cases missed by A. fumigatus-IgG. The secondary outcome was to compare clinical features and treatment outcomes of AF-CPA and NF-CPA.

Among 279 patients (mean age 45.7 ± 14.8 years, 64% male), seropositivity was 95.3% for A. fumigatus, 70.6% for A. flavus, 56.6% for A. niger and 30.5% for A. terreus. The addition of non-fumigatus-IgG increased serologic yield by 61%. NF-CPA was diagnosed in 14% (39/279), with A. fumigatus-IgG alone missing 25.6% of these cases. Treatment outcomes at six (n = 228) and 12 (n = 222) months were similar between AF-CPA and NF-CPA groups, although the percentage reduction in serum A. fumigatus-IgG was significantly greater in AF-CPA.

Incorporating non-fumigatus Aspergillus-IgG enhances the serodiagnosis of CPA. However, treatment outcomes are similar in patients with AF-CPA and NF-CPA.