PET-CT avidity and Aspergillus serology in chronic pulmonary Aspergillosis

<bold>Introduction:</bold> Chronic pulmonary aspergillosis (CPA) has an indolent presentation and variable radiological findings. Quantitative Aspergillus IgG ELISA has supplanted precipitin testing and is used in diagnosis and monitoring. The clinical relevance or prognostic value of a higher Aspergillus (Asp) IgG (Asp IgG) titre has not been evaluated. <bold>Aims:</bold> To correlate Asp IgG titres with inflammatory burden as captured on PET-CT prior to initiation of treatment for patients diagnosed with CPA. <bold>Methods:</bold> All patients who underwent a PET-CT for investigation of possible lung cancer prior to CPA diagnosis and management between March 2015 and July 2019 were reviewed at the National Aspergillosis Centre, UK. PET-CT avidity, Asp IgG, Asp IgE, total IgE, C-reactive protein, white cell count, and serum albumin were collected. Results were analysed using Spearman rank correlation methodology. <bold>Results:</bold> 13 patients were identified. No patient had a diagnosis of lung cancer. The mean levels of Asp IgG, and total IgE were 131.9 mg/L (range: 25-365 mg/L), and 731.7 kAU/L (range: 3.3-6562 kAU/L) respectively. 7 patients were Asp sensitized. PET avidity was positively correlated to Asp IgG (ρ = 0.780, p = 0.002), and negatively correlated to Asp IgE (ρ = -0.808, p = 0.003). PET avidity and serology were not otherwise significantly correlated. <bold>Conclusions:</bold> CPA patients with a higher Asp IgG titre had higher avidity on PET-CT, suggesting that Asp IgG can be used as a surrogate for the degree of inflammation in CPA lesions. Further studies should address whether this correlation persists during antifungal treatment and whether it can be used to determine optimal treatment duration.