Correlations of patch test reactivity and the repeated open application test (ROAT)/provocative use test (PUT).

The clinical relevance of patch test reactions is often difficult to determine. Use tests have been developed to further evaluate the significance of patch test results. We review studies that have defined correlations between the threshold concentrations at patch testing and the outcome of use tests for particular chemical allergens. Results of patch testing with serial dilutions of colophony, cinnamic aldehyde, and isoeugenol have shown concordance with the outcome of use tests. On the other hand, poor correlations between patch test reactivity and the use test were demonstrated in another study on isoeugenol and on studies on hydroxycitronellal, formaldehyde and chromium. These studies shed light on some factors that may influence the outcome of use tests. Individual factors such as patch test sensitivity, regional variations in reactivity and percutaneous penetration appear to play significant roles. Exposure dose, length of time of exposure, and other factors yet to be determined also affect degree of reactivity. Because patients with low thresholds in serial dilution patch testing are known to react to lower concentrations of products at use testing, results of these studies may be used to help identify subjects with a high risk of developing clinical disease. From the public health standpoint, data obtained may be used as a guide in limiting exposure concentrations in consumer products.