Diagnosis of allergic bronchopulmonary aspergillosis (ABPA) in cystic fibrosis

Background: The diagnosis of allergic bronchopulmonary aspergillosis (ABPA) in cystic fibrosis (CF) patients may be difficult to establish because ABP A shares many characteristics with coexisting atopy or other lung infection s in these patients. This study aimed to evaluate the sensitivity and speci ficity of various paraclinical parameters in the diagnosis of ABPA in patie nts with CF. Methods: Accumulated data from a 5-year period in 238 CF patients were used to divide patients into two groups designated the ABPA group (n = 26) and the non-ABPA group (n = 35). Patients in both groups were colonized with As pergillus fumigatus (Af.), but only the ABPA group consistently demonstrate d specific IgE antibodies and specific precipitins. Patients without A. fum igatus colonization were not assigned to either of these groups (n = 177). By this selection as the true diagnosis, 10 patients were selected from the ABPA group and 10 patients from the non-ABPA group. Results: The groups were comparable as to age, sex, lung function (P = 0.6) , and presence of chronic Pseudomonas aeruginosa infection (P > 0.1). No si gnificant difference between the groups in unspecific atopic parameters suc h as eosinophil count (P = 0.9) or eosinophil cationic protein (ECP) in spu tum, plasma, or serum (P = 0.9, P = 0.59, and P = 0.9, respectively) was de monstrated. Total IgE was significantly higher in the ABPA group (P < 0.01) . The groups were comparable in skin prick test (SPT) positivity to a stand ard panel of aeroallergens (pollen, dander, molds, and mites) (P > 0.2). St atistically significantly higher levels in the ABPA group were demonstrated in specific IgE to Af.: (P < 0.05), SPT positivity to Af: (P < 0.02), and Af: precipitins (P < 0.05). Histamine release (HR) to Af. tended to be high er (P = 0.075) in the ABPA group. Specific IgE to Af: was determined by Mag ic Lite (ML), CAP, and Maxisorp (in-house RAST). The CAP level was one to t wo classes higher than the ML level; however, the results were comparable ( r = 0.66, P < 0.005). IgE to Af: measured by CAP was the test which offered the highest positive predictive value (PPV) and negative predictive value (NPV). Optimal diagnostic cutoff levels for the diagnosis of ABPA were dete rmined: class 2 for HR to Af.. 200 kIU/l for total IgE, and 3.5 (titer) for precipitating antibodies to Af., and class 2 for IgE to Af: (by CAP System ). Conclusions: Unspecific atopy markers were of limited value for the diagnos is of ABPA. Patients with ABPA do not seem to be more atopic to other aeroa llergens than non-ABPA patients. The most valid parameters for the diagnosi s of ABPA in CF are SPT to Af., IgE to Af.: in combination with precipitati ng antibodies to Af., and/or total IgE.