Optimising the cut-off of the Bordier Aspergillus IgG ELISA for the diagnosis of chronic pulmonary aspergillosis

Retrospective Comparison of Two Aspergillus IgG Enzyme Immunoassays for Diagnosing Pulmonary Aspergillosis

Aspergillus-specific antibodies are diagnostic indicators of allergic bronchopulmonary aspergillosis (ABPA) and chronic pulmonary aspergillosis (CPA). Tests for detecting Aspergillus-specific antibodies were not used clinically in Japan, and the production of the Aspergillus precipitin test was discontinued. Thus, alternative tests for diagnosing aspergillosis are urgently needed. We retrospectively evaluated 64 patients with suspected ABPA and CPA who underwent precipitin antibody testing. Serum Aspergillus IgG levels were measured and compared using the Bordier Aspergillus fumigatus ELISA and the Platelia Aspergillus IgG (Bio-Rad) kits. Of the participants, 18 were diagnosed with CPA, and 8 were diagnosed with ABPA. Both the Bordier and Bio-Rad kits showed high sensitivity and specificity for CPA and ABPA. The area under the receiver operating characteristic curves for the Bordier and Bio-Rad kits were 0.97 and 0.95, respectively, for CPA, and 0.89 and 0.91, respectively, for ABPA. In contrast to the Bordier kit, the Bio-Rad kit showed relatively low anti-Aspergillus IgG levels and lower sensitivity to non-fumigatus Aspergillus infections. The Aspergillus-specific IgG ELISA tests showed sufficient diagnostic accuracy. Therefore, these assays are recommended as alternatives to the precipitin kit for diagnosing aspergillosis in clinical settings in Japan.

New estimation of the prevalence of chronic pulmonary aspergillosis (CPA) related to pulmonary TB - a revised burden for India

Background

Chronic pulmonary aspergillosis (CPA) may be confused with, or a coinfection of, pulmonary tuberculosis (PTB), or may manifest itself after completion of antituberculous therapy (ATT).

Methods

Literature searches were conducted on PubMed. The selected studies stated the timing of CPA diagnosis with respect to PTB. The key assumptions for estimating the annual incidence, annual deaths, and 5-year-period prevalence related to CPA were: of the clinically diagnosed PTB patients , 19% of those HIV-negative had CPA and 7% of HIV-positive patients had CPA; the percentage of patients presenting in the first year after PTB diagnosis or developing CPA as ATT finished was 10%; the annual rate of development of CPA from 2-5 years after PTB diagnosis was 1.5%; and the mortality of CPA was 20% in year 1 and 7.5% thereafter to year 5.

Findings

In India, the annual incidence of CPA arising in PTB patients in 2019 was estimated to be 363 601  cases (range 254 521 - 472 682) and 42 766 deaths (range 29  936-55 595) - 10.5% of total PTB deaths. The 5-year-period prevalence of CPA was estimated at   1 575 716 , with an additional 100 715 deaths' total range of deaths 100 436- 186 525) annually.

Interpretation

The revised estimation indicates a substantial unmet need for better diagnosis of CPA as part of a complex PTB-related respiratory morbidity burden.

Prospective Evaluation of Positivity Rates of Aspergillus-Specific IgG and Quality of Life in HIV-Negative Tuberculosis Patients in Lagos, Nigeria

Background

Pulmonary tuberculosis (PTB) often results in residual anatomical and functional changes despite microbiological cure and may be complicated by chronic pulmonary aspergillosis (CPA). In this study, we determined the perceived health-related quality of life (HRQoL) of patients during and after PTB therapy and compared it with their quantitative Aspergillus-specific IgG positivity rates.

Methodology

We conducted a longitudinal study among TB patients attending two directly observed therapy short-course (DOTS) clinics in Lagos, Nigeria. Two hundred and four confirmed TB patients were recruited over 9 months, with five visits at baseline and 3, 6, 9, and 12 months. They were all acid-fast bacilli smear, GeneXpert, or culture positive for Mycobacterium tuberculosis. Two HRQoL questionnaires translated into Yoruba were self-administered. Chest X-ray and Aspergillus IgG were collected at each visit.

Results

A total of 204 participants were recruited into this study. Most (70.6%) were age 18–39 years, and only 3.9% were above 60 years; 66.7% of all participants were males. A total of 189 (92.6%) participated in the 3-month assessment, 174 (85.3%) at 6 months, 139 (68.1%) at 9 months, and 99 (48.5%) at 12 months. At baseline, only 60.9% scored “good” or “very good” QoL and health on the WHOQOL-Bref, which improved to 77% at 6 months. At baseline, 10.4% had positive Aspergillus IgG levels, 15.1% at 3 months, 11.5% at 6 months, 16.7% at 9 months, and 19.3% at 12 months. Those with a positive Aspergillus IgG at 6 months had worse physical health (p = 0.001), psychological state (p = 0.002), social relationships (p = 0.006), and environmental QoL (p = 0.001) domains of the WHOQOL-Bref. Probable CPA was 10.4% at baseline and 19.3% at 6 months post-PTB therapy. Thirty-eight (18.6%) relocated after 6 months of treatment, 16 (7.8%) were lost to follow-up, and 11 (5.4%) died.

Conclusion

Our findings reveal a significant relationship between the QoL and Aspergillus IgG levels of TB patients. Further follow-up studies and additional imaging are required to determine when patients develop CPA and its clinical impact.

Standardization of Aspergillus IgG diagnostic cutoff in Nigerians

Background and objectives:

Commercial Aspergillus IgG antibody assays have become pivotal in the current diagnosis of chronic pulmonary aspergillosis (CPA). However, diagnostic cutoffs have been found to vary from manufactures’ recommendations in different settings. This study aimed to establish the Aspergillus IgG reference range among Nigerians and determine a diagnostic cutoff for CPA.

Methods:

Sera from 519 prospectively recruited healthy blood donors and 39 previously confirmed cases of CPA were analysed for Aspergillus IgG levels using the Bordier test kit (Bordier Affinity Products SA, Crissier, Switzerland). Accuracy versus cutoff profile and receiver operating characteristics (ROC) curve were analysed for both CPA cases and controls using the R-Studio (2020), (Window desktop, version 4.0.2 software with R packages “nnet” and “ROCR”).

Results:

Among healthy blood donors, 141 (27.2%) were aged 16–25 years with median (interquartile range, IQR) of 22 (20–24) years; 304 (58.6%) were aged 26–40 years with median (IQR) of 32 (29–36) years; while 74 (14.2%) were aged 41–60 years with median (IQR) of 46 (44–49.75). Median IgG level in respective age groups were 0.069 (0.009–0.181), 0.044 (0.014–0.202) and 0.056 (0.01–0.265) with no significant difference found in the three age categories (p = 0.69). The overall diagnostic cutoff for the diagnosis of CPA was 0.821 with an accuracy of 97.1% and area under the curve (AUC) = 0.986.

Conclusion:

The optimal diagnostic cutoff for diagnosing CPA in Nigerians using the Bordier kit was 0.821 which is lower than the manufacturer’s recommended cutoff of 1.0. The determination of this cutoff among Nigerians will significantly enhance accurate identification of CPA and assessment of its true burden in Nigeria.

Effect of patient immunodeficiencies on the diagnostic performance of serological assays to detect Aspergillus-specific antibodies in chronic pulmonary aspergillosis

Background

Prevalence of chronic pulmonary aspergillosis (CPA) is ~3 million patients worldwide, and detection of Aspergillus-specific antibody is a critical diagnostic component. Some patients with CPA have subtle immune deficits possibly contributing to poor Aspergillus antibody production and false negative results.

Materials/methods

We analyzed patient data from 167 cases of clinically confirmed CPA previously evaluated by ImmunoCAP Aspergillus-specific IgG EIA, Bordier ELISA and LDBio Aspergillus IgG/IgM ICT lateral flow assay, to identify deficiencies in: mannose binding lectin (MBL), IgG, IgA, IgM, IFN gamma, IL12 or IL17 production, and/or low cell marker counts (CD4, CD19, CD56). We defined patients as ‘sero-negative’ if ImmunoCAP Aspergillus IgG was consistently and repeatedly negative (<40 mg A/L). ‘Sero-positive’ was defined as all other CPA cases.

Results

We found the rate of false negatives by ImmunoCAP Aspergillus IgG EIA (n = 23) to be more prevalent in patients with immunodeficiency markers, especially multiple defects. MBL deficiency combined with low CD19 cells (p < 0.001), pneumococcal antibody levels (p = 0.043), IgM (p = 0.047) or three combined (p = 0.001–0.018) or all four together (p = 0.018) were significant. The performance LDBio Aspergillus IgG/IgM ICT appears to be relatively unaffected by immunodeficiency (92.7% of ImmunoCap sero-negatives were positive). The Bordier assay performed significantly better than the ImmunoCAP assay (P = 0.0016) for sero-negative CPA cases.

Conclusions

In select cases of CPA, ImmunoCAP EIA yields a false negative result, making serological diagnosis difficult. ImmunoCAP false negatives are more prevalent in patients with multiple immunological defects, who may still be positive with the LDBio Aspergillus ICT or Bordier EIA.

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Low or undetectable Aspergillus IgG is associated with, usually, several minor immunological defects.

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Aspergillus IgG/IgM lateral flow assay is more sensitive than ImmunoCAP for CPA with or without subtle immunodeficiency.

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CPA patients may have Aspergillus IgG detectable with different assays.