LATEX ALLERGY DIAGNOSIS - IN-VIVO AND IN-VITRO STANDARDIZATION OF A NATURAL-RUBBER LATEX EXTRACT

For the diagnosis of IgE-mediated (immediate) hypersensitivity to natu ral rubber latex (NRL), skin prick testing with extracts of latex glov es has been widely used, but such extracts are difficult to standardiz e. The present study aimed to produce on an industrial scale an NRL ex tract from freshly collected NRL and to evaluate, calibrate, and stand ardize the extract by both in vivo and in vitro testing. The source ma terial, latex of the rubber tree, Hevea brasiliensis (clone RRIM 600), was frozen immediately after collection in Malaysia and shipped in dr y ice to Stallergenes SA, France. Protein and allergen profiles were a nalyzed by sodium dodecyl sulfate polyacrylamide gel electrophoresis ( SDS-PAGE), immunoblotting, isoelectric focusing (IEF), crossed immunoe lectrophoresis (CIE), and crossed radioimmunoelectrophoresis (CRIE). A llergen quantification was effected by RAST inhibition. The capacity o f the preparation to elicit immediate hypersensitivity reactions in vi vo was measured by skin prick testing in 46 latex-allergic patients an d 76 nonallergic control subjects. SDS-PAGE and immunoblot profiles of the extract and an NRL standard (E8) provided by the US Food and Drug Administration were almost identical, disclosing several distinct IgE -binding proteins with apparent molecular weights of 14, 20, 27, 30, a nd 45 kDa, conforming to reported molecular weights of several signifi cant NRL allergens. An arbitrary index of reactivity (IR) of 100 was a ssigned to the extract at 1:200 dilution (w/v), having a protein conte nt of 22 mu g/ml. Skin prick testing of latex-allergic patients and co ntrols using the extract at 100 IR revealed 93% sensitivity, 100% spec ificity, 100% negative predictive value, and 96% positive predictive v alue. In conclusion, a skin prick test reagent for diagnosis of type I NRL allergy was successfully standardized. The reagent was demonstrat ed to contain most, if not all, of the currently known clinically sign ificant NRL allergens, and it showed high sensitivity and specificity.