Widespread immunoglobulin E-mediated hypersensitivity in the Sudan to the “green nimitti” midge, Cladotanytarsus lewisi (diptera: Chironomidae) : I. Diagnosis by radioallergosorbent test

Abstract

A radioallergosorbent test (RAST) has been developed for the diagnosis of hypersensitivity to “green nimitti” chironomid midges of the species Cladotanytarsus lewisi. There was a high percentage binding of 125 I-anti-IgE to the allergen particle complex by serum from subjects who were clinically hypersensitive, and the RAST was inhibited following incubations of allergic sera with an extract of the allergen. In 104 hypersensitive subjects (i.e., those with a positive skin test or clinical history of bronchial asthma, with or without rhinitis) and 21 controls, the RAST appeared to be specific and of diagnostic value: (1) The percentage binding was appreciably higher in 38 symptomatic individuals (group I) with strongly positive skin tests as compared with 36 patients with moderate skin reactivity (group II). (2) Seven symptomatic subjects with negative skin tests (group III) had a positive (>6% binding) green nimitti RAST. (3) Positive RASTs were demonstrable in 16 and of 17 patients with positive skin tests in whom the history was equivocal (group IV). (4) Six asymptomatic individuals with positive skin tests (group V) had low RAST values. (5) Six asymptomatic Sudanese controls with negative skin tests gave similar values to those of the group V subjects. (6) All of the sera from 15 nonatopic United Kingdom controls gave less than 6% binding of 125 I-anti-IgE. There was no statistical correlation between the concentrations of total IgE and the green nimitti RAST values. These results suggest that the RAST may be useful diagnostic test in green nimitti hypersensitivity and may also be of value in studies on the epidemiology and in the monitoring of treatment of this important and widespread allergy problem in the Sudan.