Latex protein levels in external condom catheters

The Food and Drug Administration (FDA) allows for labeling medical products that have reduced levels of total water-extractable latex protein. The standard test method of the American Society for Testing and Materials (ASTM) for analysis of latex protein in natural rubber and its products is a colorimetric assay with a precipitation step called the modified Lowry assay. In an analysis of latex external condom catheters, we have documented a significant difference in protein levels between two brands of external condoms. The modified Lowry assay is a significantly less specific method than is an immunochemical assay for measuring total water-extractable latex proteins. This nonspecificity of the modified Lowry assay makes it difficult to accurately identify medical products with extremely low levels of total water-extractable latex protein.