Pitfalls in the Diagnosis of Latex Allergy

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Background: Screening patients for latex allergy prior to surgery is an important but intensive procedure. The appropriate testing strategy for diagnosing latex (Hevea brasiliensis) allergy involves in-vitro specific IgE or skin prick testing. The sensitivity and specificity of both tests are influenced by patient-specific factors or manufacturing processes that alter the clinically relevant allergens in skin testing solutions.
Methods: Total IgE and latex-specific IgE testing was introduced as a screening test. Skin prick testing was done on patients with a high probability of latex allergy and negative specific IgE with total IgE <100kU/L. SDS-PAGE was done on the non-ammoniated latex (NAL) and newly introduced ammoniated latex (AL) reagents for the clinically relevant allergens.
Results: 51 patients had a total IgE <100 (range, 2.8-99.0kU/L), and 10% had a positive skin test. 60% of positive skin tests would have been missed with lower total IgE cut-offs of 50kU/L (6% of referrals). SDS-PAGE of the NAL solution showed 3 prominent bands with molecular weights of approximately 20, 24 and 42kDa that correlated with Hev b 6, Hev b 3 and Hev b 7/13, respectively. In contrast, the AL solution showed 3 very faint higher molecular weights bands that did not correlate with clinically relevant antigens.
Conclusions: Increasing the cut-off value of total IgE for allergen-specific IgE testing increased the sensitivity of the specific IgE test. The NAL reagent had a greater number of clinically significant allergens at higher concentrations than AL, which may have implications for the clinical sensitivity of the newer AL reagent.