CCD Inhibition Test Can Improve the Accuracy of the Detection of Pollen and Seed Food Allergen-Specific IgE in Southern China

Abstract

Objective: The presence of cross-reactive carbohydrate determinants (CCDs) may cause false-positive results in vitro allergen sIgE tests. In this paper, we focused on pollen sensitisation and its relationship with CCD in patients with respiratory allergic diseases in South China. A CCD inhibition test was conducted to assess whether patients were truly allergic to pollen or whether their sIgE was caused by a CCD cross-reaction, thus providing an important basis for clinical diagnosis and treatment.

Methods: Patients with known serologic pollen sensitization were selected, and sIgE of mugwort, tree mix 20 (willow/poplar/elm tree), common ragweed, Humulus scandens, peanut, soybean and CCD was detected via the EUROBlotMaster system. Thirteen CCD-sIgE negative patients and 33 CCD-positive patients were selected, and their serum samples were subjected to the CCD inhibition test.

Results: We found that 66.0% to 95.9% of patients sensitised to pollen and seed food allergens were co-sensitized to CCD. Additionally, 73.0% to 100% of the sIgE tests for pollen and seed food allergens turned negative after inhibition, mostly for allergens from Humulus scandens (100%, 15/15), followed by mugwort and peanut (85.2%, 23/27), ragweed (81.5%, 22/27), soybean (80.0%, 20/25), and tree pollen (73.0%, 19/26).

Conclusion: CCD causes false positives in the in vitro allergen sIgE tests of patients with respiratory allergic diseases in South China. Attention should be paid to the use of CCD inhibitors in diagnosing in vitro allergies because of their importance in diagnosing and treating local allergic diseases.

Keywords: CCD; EUROBlotMaster; cross-reactive carbohydrate determinants; false-positive; food allergen; pollen allergen; special IgE.

Figure 1

Prevalence rates and sIgE levels of CCD and plant allergens in 170 patients.

Figure 2

Relationship between plant allergen sensitisation and CCD-sIgE. (A) Radar charts of plant allergens sIgE in CCD sIgE-negative or CCD sIgE-positive patients, (B) the positivity of plant allergens sIgE in patients with different CCD classes. CCD-sIgE negative (n=91), CCD-sIgE positive (n=79), CCD-sIgE classes 1–3 (n=53), CCD-sIgE classes 4–6 (n=26).

Figure 3

Optimal scale analysis of the sIgE levels of CCD and plant allergens. The closer the distance between the points is, the greater the likelihood that they contain the same information, indicating a closer relationship between them. The close proximity of CCD and ragweed and tree pollen allergens indicated that they have the closest relationship (Cronbach’s alpha=95.6%, suitable for this analysis).

Figure 4

Changes in plant allergens before and after CCD inhibition. (A) CCD-positive patients (n=33), (B) CCD-negative patients (n=17). **P<0.01, the positivity rate before and after inhibition was significantly different.

Figure 5

The scatter diagram of plant allergen sIgE classes before or after CCD inhibited. (A) for mugwort (CCD positive/negative n=27/6), (B) for common ragweed (CCD positive/negative n=27/2), (C) for tree mix pollen (CCD positive/negative n=26/5), (D) for soybean (CCD positive/negative n=25/8), (E) for peanut (CCD positive/negative n=27/6), (F) for Humulus scandens (CCD positive/negative n=15/4).