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

Background 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. Methods 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. Results 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. Conclusions Incorporating non‐fumigatus Aspergillus ‐IgG enhances the serodiagnosis of CPA. However, treatment outcomes are similar in patients with AF‐CPA and NF‐CPA.