|LETTER TO THE EDITOR
|Year : 2012 | Volume
| Issue : 2 | Page : 89-90
Making the case for using the Aspergillus immunoglobulin G enzyme linked immunoassay than the precipitin test in the diagnosis of allergic bronchopulmonary aspergillosis
Sujoy Khan1, Suresh Ramasubban2, Chinmoy K Maity3
1 Department of Allergy and Immunology, Apollo Gleneagles Hospital, Kolkata, India
2 Department of Chest Medicine, Apollo Gleneagles Hospital, Kolkata, India
3 Department of Medicine, Apollo Gleneagles Hospital, Kolkata, India
|Date of Web Publication||27-May-2013|
Department of Allergy and Immunology, Apollo Gleneagles Hospital, 58 Canal Circular Road, Kolkata - 700 054
|How to cite this article:|
Khan S, Ramasubban S, Maity CK. Making the case for using the Aspergillus immunoglobulin G enzyme linked immunoassay than the precipitin test in the diagnosis of allergic bronchopulmonary aspergillosis. Indian J Allergy Asthma Immunol 2012;26:89-90
|How to cite this URL:|
Khan S, Ramasubban S, Maity CK. Making the case for using the Aspergillus immunoglobulin G enzyme linked immunoassay than the precipitin test in the diagnosis of allergic bronchopulmonary aspergillosis. Indian J Allergy Asthma Immunol [serial online] 2012 [cited 2014 Jul 31];26:89-90. Available from: http://www.ijaai.in/text.asp?2012/26/2/89/112555
We read with interest the report by Dr. Agarwal et al. of a patient with chronic obstructive pulmonary disease and allergic bronchopulmonary aspergillosis (ABPA) and agree with the authors' view that the ochterlony counter immunoelectrophoresis (CIE) test (or the precipitin test) is not only insensitive,  but also subject to inter-observer variability. We briefly describe three studies that argue why the Aspergillus immunoglobulin G (IgG) by enzyme linked immune assay (ELIA) should replace the precipitin test. Clinicians should also refer to the Patterson's criteria for ABPA as unavailability of the precipitin test should not deter clinicians from confidently diagnosing APBA in patients with unusual obstructive airway disease.
Baxter et al. assessed the performance of two commercial ELIAs for detection of Aspergillus IgG antibodies and with the precipitin test (CIE titer) on 175 adult patients with chronic pulmonary aspergillosis or ABPA.  The commercial ELIA kits (Phadia ImmunoCAP and Bio-Rad Platelia Aspergillus IgG) had good agreement with sensitivities between 97% and 93%, respectively, but the concentrations of antibodies were not equivalent between the assays or with the precipitin test. The inter-assay coefficient of variation for ImmunoCAP IgG was 5%, whereas for Platelia IgG was 33%. The direction of change of the CIE titre over 6 months was observed more with the Phadia ImmunoCAP IgG levels (92% of patients) than with the Platelia IgG (72%).
Van Hoeyveld et al. showed that the agreement between the ImmunoCAP and the precipitin technique was of moderate concordance (kappa, 0.46 for both Aspergillus fumigatus and pigeon antibodies; for complete agreement Cohen's kappa coefficient is 1.0), and high levels of antibody concentrations were detected by the ImmunoCAP method in patients with ABPA or hypersensitivity pneumonitis.  Thus, the ImmunoCAP method was able to robustly detect exposure to antigens and Aspergillus IgG levels were substantially higher than in patients without antigen contact and therefore, suitable for monitoring disease activity.
Barton et al. tried to answer a more difficult question as to what defined a significant Aspergillus IgG value given that all of us are exposed to this ubiquitous antigen. Sera from patients with cystic fibrosis (CF) with/without ABPA were tested for Aspergillus IgG by ImmunoCAP method.  Patients with CF-ABPA had mean Aspergillus IgG at 132.5 mg/L (compared to patients with no or incomplete ABPA mean value 51.1 mg/L) and ROC analysis adjudged a cut-off value of 90 mg/L (sensitivity 91%, specificity 88.0%) for the diagnosis of ABPA. However, this (cut-off) value needs to be ideally decided by the local laboratory in the correct clinical context and close collaboration with respiratory and intensive-care physicians.
In this era of molecular diagnostics, specific IgE against recombinant Aspergillus antigens are now available (rAspf4 and rAspf6) with much higher sensitivity and specificity (rAspf4 IgE sensitivity 92% specificity 94%) than existing markers.  We therefore, think that the current ImmunoCAP ELIA for IgE and IgG against Aspergillus should replace the precipitin test in the diagnosis of ABPA.
| References|| |
|1.||Agarwal K, Chowdhary A, Gaur SN. A rare case of allergic bronchopulmonary aspergillosis in a patient with chronic obstructive pulmonary disease. Indian J Allergy Asthma Immunol 2012;26:20-4. |
|2.||Baxter CG, Denning DW, Jones AM, Todd A, Moore CB, Richardson MD. Performance of two Aspergillus IgG EIA assays compared with the precipitin test in chronic and allergic aspergillosis. Clin Microbiol Infect 2013;19:E197-204. |
|3.||Van Hoeyveld E, Dupont L, Bossuyt X. Quantification of IgG antibodies to Aspergillus fumigatus and pigeon antigens by ImmunoCAP technology: An alternative to the precipitation technique? Clin Chem 2006;52:1785-93. |
|4.||Barton RC, Hobson RP, Denton M, Peckham D, Brownlee K, Conway S, et al. Serologic diagnosis of allergic bronchopulmonary aspergillosis in patients with cystic fibrosis through the detection of immunoglobulin G to Aspergillus fumigatus. Diagn Microbiol Infect Dis 2008;62:287-91. |
|5.||Fricker-Hidalgo H, Coltey B, Llerena C, Renversez JC, Grillot R, Pin I, et al. Recombinant allergens combined with biological markers in the diagnosis of allergic bronchopulmonary aspergillosis in cystic fibrosis patients. Clin Vaccine Immunol 2010;17:1330-6. |