Delayed-Type Hypersensitivity Skin Testing: Variance Among Candida albicans Extracts

To the Editor. —  Accurate assessment of cellular immune response by delayed hypersensitivity skin testing requires skin-test materials of defined quality. This type of skin testing provides important information about cellular aspects of the immune system and the ability to process and present antigen to cellular effector cells. Certain delayedtype skin-testing materials are regulated by the Center for Biologics Evaluation and Research of the Food and Drug Administration to ensure consistent potency. Candida albicans is an important antigen, but only one product with guaranteed potency exists, the Merieux "Multi-Test CMI." This product delivers Candida and other extracts by multiple percutaneous puncture. Many physicians have preferred standard intradermal techniques because more predictable amounts of antigen are delivered intradermally.Extracts of fungal species contain diverse antigens and may differ substantially in content. Thus, equivalence is difficult to ensure. With antigens not licensed for delayed-type hypersensitivity skin testing, practitioners generally select materials licensed