LATEX-SPECIFIC IGE, SKIN TESTING, AND LYMPHOCYTE-TRANSFORMATION TO LATEX IN LATEX ALLERGY

Background: This study was designed to determine the discriminative va lue of latex-specific IgE tests, latex skin tests, and lymphocyte tran sformation tests (LTTs) to latex in 38 patients with latex allergy (12 nonatopic and 26 atopic) and 44 control subjects (24 nonatopic and 20 atopic). We also evaluated the recommended positive cutoff (i.e., 0.3 5 kU/L) of both in vitro latex-IgE tests. Methods: Latex-specific IgE levels were determined by the Immuno-CAP (Upjohn-Pharmacia) and the AL aSTAT-RIA (Diagnostic Products Corp.) assays, Skin tests and LTTs were performed with a nonammoniated latex extract (DPC). Sensitivities and specificities were defined according to the 95th percentile value of nonatopic control subjects, For the in vitro IgE tests, sensitivity an d specificity were also calculated by using the proposed positive thre shold of 0.35 kU/L. Sensitivities and specificities of both cutoffs we re compared. Results: Compared with a clinical history of latex allerg y and according to the 95th percentile value of nonatopic control subj ects (0.44 kU/L), latex-specific IgE determined by the Immuno-CAP assa y achieved a sensitivity of 97% and a specificity of 86%. For the ALaS TAT-RIA assay, with 0.54 kU/L as the 95th percentile threshold value i n nonatopic control subjects, sensitivity was 100%, and specificity wa s 83%. According to the threshold value of 0.35 kU/L, a sensitivity of 97% and a specificity of 83% for the Immuno-CAP assay and a sensitivi ty of 100% and a specificity of 33% for the ALaSTAT-RIA assay were obs erved. The latex skin test reached a sensitivity of 97% and a specific ity of 100%. The LTT to latex showed a sensitivity of 39% and a specif icity of 95%. No relation between symptoms and latex-specific IgE test s, latex skin tests, or LTTs nas found. Conclusions: Our results confi rm that latex skin tests and latex-specific IgE assessments are sensit ive and specific methods for establishing the diagnosis of latex aller gy, although the specificity of the ALaSTAT-RIA assay was very low whe n interpreted according to the threshold of 0.35 kU/L. The LTT to nona mmoniated latex is too insensitive for diagnosis of allergy to latex T his reemphasizes that in order to evaluate the sensitivity and specifi city of diagnostic procedures, one should always include an appropriat e control group.