DIAGNOSIS OF NATURAL-RUBBER LATEX ALLERGY - MULTICENTER LATEX SKIN TESTING EFFICACY STUDY

Background: No characterized diagnostic natural rubber latex skin test ing material is licensed for use in the United States. Objective: We h ave conducted a multicenter clinical skin testing study to document th e safety and diagnostic sensitivity and specificity of a candidate Hev ea brasiliensis nonammoniated latex (NAL) extract. These data are inte nded to support the licensing of this reagent for the diagnosis of lat ex allergy in high-risk populations, Methods: Three hundred twenty-fou r subjects (304 adults and 20 children) were classified by their clini cal history as having latex allergy (LA group: 124 adults and 10 child ren) or having no latex allergy (NLA group, 180 adults and 10 children ). All subjects provided blood samples and then received sequential pu ncture skin tests (PSTs) at 1, 100, or 1000 mu g/mL protein with a bif urcated needle and NAL (Greer Laboratories) from Malaysian Hevea brasi liensis (clone 600) sap. A 2-stage glove provocation test was used to clarify latex allergy status of individuals with positive history/nega tive PST result and negative history/positive PST result mismatches. R esults: Twenty-four subjects (15%) originally designated as having LA on the basis of their initial clinical history were reclassified to th e NLA group on the basis of a negative glove provocation test result. Of the 134 subjects with LA, 51 (40%) were highly sensitive to latex, with a positive PST result at 1 mu g/mL NAL, The Greer NAL reagent pro duced a positive PST rate (sensitivity) of 95% and 99% in subjects wit h LA at 100 mu g/mL and 1 mg/mL, respectively, The negative PST rate ( specificity) in 190 subjects with a negative history with the NAL extr act at 100 mu g/mL and 1 mg/mL was 100% and 96%, respectively. Immedia tely after the PST, mild systemic reactions (mainly pruritus) were rec orded in 16.1% of the adults in the LA group and 4.4% of the adults in the NLA group. No reactions required treatment with epinephrine. Only mild delayed reactions were observed in 9.6% (LA group) and 2.8% (NLA group) of subjects 24 to 48 hours after PST. Mean wheal and erythema diameters measured in the 10 children in the LA group with spina bifid a at 100 mu g/mL and I mg/mL were similar to those observed in the adu lts in the LA group, suggesting that children are not at increased ris k for systemic reactions compared with adults. Conclusions: A suggesti ve clinical history is necessary but not sufficient for a definitive d iagnosis of IgE-dependent latex allergy. These data support the safety and diagnostic efficacy of the Greer NAL skin test reagent at 100 mu g/mL and 1 mg/mL for confirmatory PSTs.