OBJECTIVE Chronic pulmonary aspergillosis (CPA) is estimated to affect 3 million persons worldwide. Aspergillus-specific IgG is a key component in CPA diagnosis. We aimed to establish the optimal diagnostic cut offs for CPA and the comparative performance of six assays in this context. METHODS Sera from 241 patients with CPA and 100 healthy blood donors were tested using five Aspergillus-specific IgG assays plus precipitin testing using Microgen Aspergillus antigens. RESULTS Receiver operating characteristic (ROC) curve area under the curve (AUC) results were as follows: ThermoFisher Scientific ImmunoCAP 0.996 (95% confidence interval 0.992-1), Siemens Immulite 0.991 (0.982-1), Serion 0.973 (0.960-0.987), Dynamiker 0.918 (0.89-0.946) and Genesis 0.902 (0.871-0.933). Optimal CPA diagnostic cut-offs were; ImmunoCAP 20 mg/L (96% sensitivity, 98% specificity), Immulite 10 mg/L (96% sensitivity, 98% specificity), Serion 35 U/ml (90% sensitivity, 98% specificity), Dynamiker 65 AU/ml (77% sensitivity, 97% specificity) and Genesis 20 U/ml (75% sensitivity, 99% specificity). The precipitin test was 59% sensitive and 100% specific. CONCLUSIONS ImmunoCAP and Immulite were statistically significantly superior to the other assays. Precipitins testing performed poorly. The currently accepted ImmunoCAP cut-off of 40 mg/L appears sub-optimal for CPA diagnosis and may require revision in this context.