The clinical utility of IgE against recombinant Aspergillus fumigatus-specific (rAsp) antigens in allergic bronchopulmonary aspergillosis (ABPA) remains unclear.
To identify the optimal diagnostic cut-offs of rAsp-specific IgE in differentiating ABPA from A.fumigatus-sensitized asthma (ASA), and define their utility in the diagnosis of ABPA.
We enrolled consecutive subjects of ASA and ABPA. IgE against rAsp f1, f2, f3, f4, and f6 was assayed in all the subjects. We evaluated three fixed cut-offs (0.35, 0.5, and 1.0 kUA/L) for their diagnostic performance in the entire cohort. We also divided the study population into derivation and validation cohorts. Cut-offs for rAsp-specific IgE were obtained using the receiver operating characteristic (ROC) analysis in the derivation cohort. We then evaluated the diagnostic performance of these cut-offs in the validation cohort. We further correlated rAsp-specific IgE levels in ABPA with asthma control, spirometry, imaging, and immunological markers.
We included 194 subjects (123 ABPA and 71 ASA). The statistically derived cut-offs proved superior to fixed cut-offs. IgE against rAsp f1 yielded the best combination of sensitivity (89%) and specificity (100%). The sensitivity and specificity of IgE against either rAsp f1 (cut-off, 4.465 kUA/L) or f2 (cut-off, 1.300 kUA/L) for diagnosing ABPA was 100% and 81%, respectively. The correlation between rAsp-specific IgE and most clinical parameters of ABPA was weak.
IgE against rAsp f1 and f2 (using ROC derived cut-offs) were found to be the most useful in differentiating ABPA from ASA. Due to conduct at single-center, our results require further validation.
ABPM; allergic fungal airway disease; allergy; asthma; component-resolved diagnostics; fungal sensitization; molecular allergology; molecular diagnostics.