Patch testing with a standard allergen ("screening") tray: rewards and risks.

The TRUE Test panels, which are the only patch testing devices approved by the Food and Drug Administration in the US, consist of 24 patches, one of which is a negative control. The remaining 23 patches contain 42 unique allergens and four complex mixtures. Although these panels contain approximately 1.4% of the > 3700 known allergens, they perform robustly in detecting allergic contact dermatitis (ACD). Twenty-eight percent of patients are fully evaluated by application of TRUE Test((R)). The present paper reviews the appropriate use of the TRUE Test panels. The need to determine relevance of any positive reaction is stressed. The common causes of false-positive and false-negative reactions are outlined. Those product types where the TRUE Test panels detect the majority of relevant allergic reactions are reviewed, as are the other sources of exposure to the allergens on these panels. The impact of ACD on quality of life is significant. Only by patch testing can the diagnosis be made.