A rapid test for soy aeroallergens exposure assessment

Abstract

Background: Determining soy aeroallergens levels is extremely important in the assessment of health risks due to these airborne substances. Currently, soy aeroallergens exposure in the environment is monitored using enzyme immunoassays (EIA) which must be evaluated in a specialized laboratory by skilled personnel.

Objective: To describe the development and performance of a rapid immunochromatography assay for the detection of soy aeroallergens in environmental samples.

Methods: A test strip using gold labeled anti-soy hull low molecular weight extract (SHLMWE) antibody for the rapid detection of soy aeroallergens in environmental samples was developed. One hundred nineteen airborne samples were analysed in parallel by the strip assay and the anti-SHLMWE sandwich EIA. The assay results were visually analysed by three independent observers who ranked samples as: -, + or ++. Strips were also scanned and analysed by densitometry.

Results: The rapid test detected a range of concentrations from 6.25 to 25 ng/mL. Agreement in strip assay interpretations between evaluators was substantial (Kappa = 0.63; CI 0.544-0.715). Visual interpretation also gave a good concordance with EIA results, with sensitivity ranging from 77.3 to 100 and specificity from 65 to 83.5 depending on the observer. Furthermore, a strong correlation was observed between densitometry results of strip assay and EIA determinations.

Conclusions: The strip assay developed is rapid, simple, and sensitive and does not require expensive equipment or specific skills. It has considerable potential in the environmental monitoring field for screening soy aeroallergens levels in port cities where allergen measurements are not currently performed. Due to its simplicity, the test will improve the management of soy allergic patients by controlling environmental allergen exposure without the need for apparatus or skilled personnel.

Figure 1. Schematic diagram of the strip assay: 1A) Assembly of the immunostrip; 1B) Dipping of the strip; 1C) Binding of gold labeled antibody and gold labeled antibody-SHLMWE complex to control and test line respectively.

Figure 2. Three-point standard curve of SHLWE used as a source for comparison to rank the line seen on the strips as negative, positive or double positive.

The figure shows scanned strips and density analysis of the strips.

Figure 3. A typical strip assay standard curve to determine the limit of detection of the assay: 3A) Scanned strips at test line level; 3B) Graph of densitometry results (means ± SEM) at the indicated concentrations of SHLMWE using a four parameter logistic curve fit.

Figure 4. Densitometry results of strip assay and EIA determinations and EIA results by strip assay visual interpretation category.

The dashed lines indicate the EH-TLV of 627 ng/ml. 4A) Scatter plot showing the correlation between SHLMW allergens concentrations and density values of strip assay; 4B) Densitometry results by EIA result category (higher or lower than the EH-TLV).* p<0.0001; EIA results by strip assay visual interpretation category: 4C) Observer 1; 4D) Observer 2; 4E) Observer 3.