Measurement of natural rubber proteins in latex glove extracts: Comparison of the methods

Background: Healthcare workers and individuals with frequent contact with latex are at risk for latex protein allergy. Objective: The purpose of this study was to compare several established methods for measuring protein in extracts from latex-containing medical devices. Methods: Extracts from latex gloves were analyzed for natural rubber proteins using a modified Lowry assay and two different immunochemical assays. The immunochemical methods were competitive inhibition assays that employed either immune rabbit serum or human serum with antibodies directed against natural rubber proteins. Results: Seventy extracts representing five different brands of gloves from four manufacturers were analyzed. A good linear correlation (R = 0.88) was found between the immunoassay methods. Correlation to the modified Lowry method was not possible because many of the samples were below the limit of detection for the Lowry assay. Reference extracts and antisera were further characterized by Western blot analysis. The data demonstrate that the proteins recognized by rabbit antisera and the proteins recognized by human IgE are similar. The greatest difference in the immunochemical assays appears to be the relative binding of the antibody sources to high and low molecular weight natural rubber proteins in the reference extracts. Conclusions: The immunochemical assays are specific for latex proteins and provide a more sensitive and biologically relevant method for determining protein levels in latex medical products.