Cross-reactivity between cockroach and ladybug using the radioallergosorbent test.

BACKGROUND

Home infestations from Harmonia axyridis (ladybug) occur throughout the United States. IgE-mediated sensitization with allergic disease has been reported. The prevalence of ladybug sensitization has been studied by questionnaire and allergy testing in patients diagnosed as having allergic disease. Cross-reactivity with cockroach exists.

OBJECTIVES

To determine the prevalence of ladybug specific IgE in the general population by specific IgE immunoassay and to examine cross-reactivity to cockroach.

METHODS

An experimental solid phase for use in immunoassay was prepared using a ladybug extract, and performance characteristics were determined. Serum samples from 100 adult blood bank donors were tested using the ladybug specific IgE immunoassay. Known ladybug IgE-positive serum samples obtained from symptomatic patients were used to study crossreactivity with German cockroach by specific IgE immunoassay inhibition.

RESULTS

The mean background response of the assay solid phase was 51 fluorescent units with an analytical cutoff of 59 fluorescent units. It was estimated that a response of 88 fluorescent units corresponds to a specific IgE concentration of 0.1 kUa/L. The extinction dilution curve was linear to 0.1 kUa/L. The assay cutoff was set at 0.1 kUa/L. Of the 100 blood donor serum samples, 10 were positive for ladybug specific IgE. Inhibition assays revealed partial cross-reactivity with German cockroach.

CONCLUSION

Although an immunoassay solid phase prepared with ladybug whole body extract will identify persons in a general population sensitized to epitopes found in the extract, clinicians performing allergy testing using whole body ladybug extract should be aware that a positive result may or may not indicate that exposure to actual ladybug allergens is causing sensitization.