Abstract
AimThe efficiency of various investigations and diagnostic criteria used in diagnosis of allergic bronchopulmonary aspergillosis (ABPA) remain unknown, primarily because of the lack of a gold standard. Latent class analysis (LCA) can provide estimates of sensitivity and specificity in absence of gold standard. Herein, we report the performance of various investigations and criteria employed in diagnosis of ABPA.MethodsConsecutive subjects with asthma underwent all the following investigations Aspergillus skin test, IgE levels (total and A.fumigatus specific), Aspergillus precipitins, eosinophil count, chest radiograph, and high-resolution computed tomography (HRCT) of the chest. We used LCA to estimate the performance of various diagnostic tests and criteria in identification of ABPA.ResultsThere were 372 asthmatics with a mean age of 35.9 years. The prevalence of Aspergillus sensitization was 53.2%. The sensitivity and specificity of various tests were Aspergillus skin test positivity (94.7%, 79.7%); IgE levels>1000 IU/mL (97.1%, 37.7%); A.fumigatus specific IgE levels>0.35 kUA/L (100%, 69.3%); Aspergillus precipitins (42.7%, 97.1%); eosinophil count>1000 cells/µL (29.5%, 93.1%); chest radiographic opacities (36.1%, 92.5%); bronchiectasis (91.9%, 80.9%); and, high-attenuation mucus (39.7%, 100%). The most accurate criteria was the Patterson criteria using six components followed by the Agarwal criteria. However, there was substantial decline in accuracy of the Patterson criteria if components of the criteria were either increased or decreased from six.Conclusions A.fumigatus specific IgE levels and high-attenuation mucus were found to be the most sensitive and specific test respectively in diagnosis of ABPA. The Patterson criteria remain the best diagnostic criteria however they have good veridicality only if six criteria are used.
Highlights
Allergic bronchopulmonary aspergillosis (ABPA) is a pulmonary disorder caused by immunologic reactions to antigens released by Aspergillus fumigatus, colonizing the airways of patients with asthma and cystic fibrosis. [1,2] The disease presents with uncontrolled asthma, expectoration of mucus plugs, fleeting pulmonary opacities and bronchiectasis
To overcome some of the limitations of the Patterson criteria, we have proposed new criteria wherein greater emphasis has been laid on specific components in the diagnosis of ABPA, such as total and A. fumigatus specific IgE levels
As the currently used diagnostic criteria are a composite of the aforementioned diagnostic tests, [9,11] conventional statistical methods would lead to erroneous estimates of sensitivity and specificity because investigations like skin test and IgE levels that are integral part of the criteria will have perfect (100%) sensitivity values
Summary
Allergic bronchopulmonary aspergillosis (ABPA) is a pulmonary disorder caused by immunologic reactions to antigens released by Aspergillus fumigatus, colonizing the airways of patients with asthma and cystic fibrosis. [1,2] The disease presents with uncontrolled asthma, expectoration of mucus plugs, fleeting pulmonary opacities and bronchiectasis. [3] The community prevalence of ABPA complicating asthma is speculated to be about 1–2%, [4] with a global burden of about 5 million patients. [5] The prevalence of ABPA is even higher in the asthma clinics where it was estimated to be about 13%. [6] The diagnosis of ABPA is currently made on the combination of clinical, radiological and immunological findings. [7] Almost six decades have elapsed since its first description, yet there is no consensus on the diagnostic criteria for identification of ABPA. [8] The Patterson criteria are the most often used yardstick for diagnosis of ABPA, [9,10] and utilize the following investigations in asthmatic patients, namely Aspergillus skin test, IgE levels (total and A. fumigatus specific), eosinophil count, Aspergillus precipitins, radiographic pulmonary opacities and bronchiectasis. [8] The Patterson criteria are the most often used yardstick for diagnosis of ABPA, [9,10] and utilize the following investigations in asthmatic patients, namely Aspergillus skin test, IgE levels (total and A. fumigatus specific), eosinophil count, Aspergillus precipitins, radiographic pulmonary opacities and bronchiectasis. [14,15,16] In this study, we report the diagnostic accuracy of two diagnostic criteria (Patterson et al [9] and Agarwal et al [11]) and various tests (Aspergillus skin test, serum IgE levels [total and A. fumigatus specific], eosinophil count, Aspergillus precipitins, chest radiograph, bronchiectasis and high-attenuation mucus) used in identification of ABPA, using LCA Several studies have used LCA for the evaluation of diagnostic tests where no gold standard exists, and have found this model to provide realistic estimates of the performance of diagnostic tests. [14,15,16] In this study, we report the diagnostic accuracy of two diagnostic criteria (Patterson et al [9] and Agarwal et al [11]) and various tests (Aspergillus skin test, serum IgE levels [total and A. fumigatus specific], eosinophil count, Aspergillus precipitins, chest radiograph, bronchiectasis and high-attenuation mucus) used in identification of ABPA, using LCA
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