Establishing Aspergillus-Specific IgG Cut-Off Level for Chronic Pulmonary Aspergillosis Diagnosis: Multicenter Prospective Cohort Study

Diagnosis of Chronic Pulmonary Aspergillosis: Clinical, Radiological or Laboratory?

Chronic pulmonary aspergillosis (CPA) is a chronic progressive lung disease associated with a poor prognosis and a 5-year mortality rate of approximately 40-50%. The disease is characterized by slowly progressive destruction of the lung parenchyma, in the form of multiple cavities, nodules, infiltrates or fibrosis. CPA can be challenging to diagnose due to its non-specific symptoms and similarities with other respiratory conditions combined with the poor awareness of the medical community about the disease. This can result in delayed treatment even for years and worsening of the patient's condition. Serological tests certainly play a significant role in diagnosing CPA but cannot be interpreted without radiological confirmation of CPA. Although many data are published on this hot topic, there is yet no single definitive test for diagnosing CPA, and a multidisciplinary approach which involves a combination of clinical picture, radiological findings, microbiological results and exclusion of other mimicking diseases, is essential for the accurate diagnosis of CPA.

Comparison of diagnostic efficiency of detecting IgG and IgE with immunoassay method in diagnosing ABPA: a meta-analysis

BACKGROUND

Hitherto, the bulk of diagnostic criteria regards Aspergillus-specific immunoglobulin E as a key item, and regard IgG as an auxiliary method in diagnose. Nevertheless, there is no conclusive study in summarize the performance of IgG and IgE diagnosing ABPA.

METHODS

We conducted a systematic review to identify studies report results of IgE and IgG detection in diagnosing ABPA. QUADAS-2 tool was used to evaluate included studies, and we applied the HSROC model to calculate the pooled sensitivity and specificity. Deeks' funnel was derived to evaluated the public bias of included studies, and Cochrane Q test and I2 statistic were used to test the heterogeneity.

RESULTS

Eleven studies were included in this study (1127 subjects and 215 for IgE and IgG). Deeks's test for IgE and IgG were 0.10 and 0.19. The pooled sensitivity and specificity for IgE were 0.83 (95%CI: 0.77, 0.90) and 0.89 (0.83, 0.94), and for IgG were 0.93 (0.87, 0.97) and 0.73 (0.62,0.82), with P value < 0.001. The PLR and NLR for IgE were 7.80 (5.03,12.10) and 0.19 (0.13,0.27), while for IgG were 3.45 (2.40,4.96) and 0.09 (0.05,0.17). The combined diagnostic odds ratio and diagnostic score were 41.49 (26.74,64.36) and3.73 (3.29,4.16) for IgE, respectively, and were 38.42 (19.23,76.79) and 3.65 (2.96,4.34) for IgG.

CONCLUSION

The sensitivity for IgG diagnosing ABPA is higher than IgE, while the specificity for IgE is higher. IgG might be able to play a more important role in filtering ABPA patients.

Serum Aspergillus-specific IgE, IgG and IgG4 immunoglobulins assessment in the work-up of invasive pulmonary aspergillosis: a prospective cohort study

BACKGROUND

Positive microbiological fungal culture from bronchoalveolar-lavage-fluid (BAL) for Aspergillus or tissue biopsy and the detection of high levels of Aspergillus Galactomannan (GM) are commonly considered standard for diagnosing Invasive Pulmonary Aspergillosis (IPA). However, Aspergillus infection induces both cellular and humoral immune responses, characterized by the production of specific immunoglobulins, which can be easily detected in serum and accurately measured. This study hypothesized that Aspergillus-specific IgE, IgG, including IgG<inf>4</inf>, assays could be adopted as a rapid preliminary screening tool in patients with suspected Aspergillus-related lung disease in order to help in the identification of patients who require more invasive procedures (bronchoscopy, biopsy).

METHODS

We prospectively stored 447 serum specimens of patients admitted for suspected IPA from 1 January 2010 to 31 July 2021. Serum total IgE and serum IgE, IgG and IgG<inf>4</inf> specific for Aspergillus fumigatus and Aspergillus niger were determined for each sample. In addition, bronchoscopy with BAL for microbiologic culture and Aspergillus Galactomannan (GM) antigen were performed in all patients.

RESULTS

Patients with IPA, diagnosed by detection of a positive BAL culture for Aspergillus and/or a positive GM, showed higher serum levels of specific Aspergillus fumigatus and Aspergillus niger immunoglobulins. Serum-specific Aspergillus fumigatus IgG at a cut-off of 22.6 mgA/L showed the highest sensitivity in predicting IPA, though quite moderate (AUC 0.62). Nonetheless, the simultaneous presence of values below the cut-off of Aspergillus IgE, IgG and IgG<inf>4</inf> showed a negative predictive value greater than 90% both towards positive BAL culture and positive GM.

CONCLUSIONS

In patients with suspected IPA, Aspergillus-specific immunoglobulins assay could be tested as a preliminary screening tool to support more invasive procedures, i.e. BAL.

Comparison of Aspergillus-specific antibody cut-offs for the diagnosis of aspergillosis

Background

Aspergillus diseases are frequently encountered in patients who are immunocompromised. Without a prompt diagnosis, the clinical consequences may be lethal. Aspergillus-specific antibodies have been widely used to facilitate the diagnosis of Aspergillus diseases. To date, universally standardized cut-off values have not been established. This study aimed to investigate the cut-off values of Aspergillus-specific antibodies and perform a narrative review to depict the geographic differences in the Taiwanese population.

Methods

We analyzed enrolled 118 healthy controls, 29 patients with invasive aspergillosis (IA), chronic pulmonary aspergillosis (CPA), and allergic bronchopulmonary aspergillosis (ABPA) and 99 with disease control, who were tested for Aspergillus fumigatus and Aspergillus niger-specific IgG and IgE using ImmunoCAP. 99 participants not fulfilling the diagnosis of IA, CPA, and ABPA were enrolled in the disease control group. The duration of retrieval of medical records from June 2018 to September 2021. Optimal cut-offs and association were determined using receiver operating characteristic curve (ROC) analysis.

Results

We found that patients with CPA had the highest A. fumigatus-specific IgG levels while patients with ABPA had the highest A. fumigatus-specific IgE, and A. niger-specific IgG and IgE levels. In patients with CPA and ABPA, the optimal cut-offs of A. fumigatus-specific IgG and A. niger-specific IgG levels were 41.6, 40.8, 38.1, and 69.9 mgA/l, respectively. Geographic differences in the cut-off values of A. fumigatus-specific IgG were also noted. Specifically, the levels were different in eco-climatic zones.

Conclusion

We identified the optimal cut-offs of Aspergillus-specific antibodies to facilitate a precise diagnosis of aspergillosis. The observed geographic differences of the antibody levels suggest that an eco-climatic-specific reference is needed to facilitate a prompt and accurate diagnosis of aspergillosis.

Efficacy of LD Bio Aspergillus ICT Lateral Flow Assay for Serodiagnosis of Chronic Pulmonary Aspergillosis

Background: The diagnosis of CPA relies on the detection of the IgG Aspergillus antibody, which is not freely available, especially in resource-poor settings. Point-of-care tests like LDBio Aspergillus ICT lateral flow assay, evaluated in only a few studies, have shown promising results for the diagnosis of CPA. However, no study has compared the diagnostic performances of LDBio LFA in setting of tuberculosis endemic countries and have compared it with that of IgG Aspergillus. Objectives: This study aimed to evaluate the diagnostic performances of LDBio LFA in CPA and compare it with existing the diagnostic algorithm utilising ImmunoCAP IgG Aspergillus. Methods: Serial patients presenting with respiratory symptoms (cough, haemoptysis, fever, etc.) for >4 weeks were screened for eligibility. Relevant investigations, including direct microscopy and culture of respiratory secretions, IgG Aspergillus, chest imaging, etc., were done according to existing algorithm. Serums of all patients were tested by LDBio LFA and IgG Aspergillus (ImmunoCAP Asp IgG) and their diagnostic performances were compared. Results: A total of 174 patients were included in the study with ~66.7% patients having past history of tuberculosis. A diagnosis of CPA was made in 74 (42.5%) of patients. The estimated sensitivity and specificity of LDBio LFA was 67.6% (95% CI: 55.7−78%) and 81% (95% CI: 71.9−88.2%), respectively, which increased to 73.3% (95% CI: 60.3−83.9%) and 83.9% (95% CI: 71.7−92.4%), respectively, in patients with a past history of tuberculosis. The sensitivity and specificity of IgG Aspergillus was 82.4% (95% CI: 71.8−90.3%) and 82% (95% CI: 73.1−89%); 86.7% (95% CI: 75.4−94.1%) and 80.4% (95% CI: 67.6−89.8%), in the whole group and those with past history of tuberculosis, respectively. Conclusions: LDBio LFA is a point-of-care test with reasonable sensitivity and specificity. However, further tests may have to be done to rule-in or rule-out the diagnosis of CPA in the appropriate setting.