Saline Vehicle Increases the Ability of Drug Patch Test in Cutaneous Adverse Drug Reactions

Abstract

Background: Drug patch test to identify cutaneous adverse drug reactions (CADRs) has been widely reported. Appropriate vehicles can improve the ability of drug delivery and significantly increase positive reaction of drug patch tests. Objective: The aim of this study was to evaluate the efficacy of drug patch tests using 0.9% saline vehicle in comparison with other traditional vehicles in CADRs. Method: All patients were patch tested with suspected drugs using 10–30% concentration of the commercialized form of drugs diluted in 0.9% saline, petrolatum, and water. Result: Of 100 patients with CADRs, 54 of those had at least one positive drug patch test. In terms of vehicles used, 43 patients had positive drug patch test with saline as compared to 35 with water (p = 0.485) and 25 with petrolatum (p = 0.007). Among CADRs subgroup, saline rendered significantly higher positive rate when compared with petrolatum in drug rash with eosinophilia and systemic symptom (DRESS) (70% vs. 20%, p = 0.025), maculopapular rash (MP) (52.4% vs. 31%, p = 0.046), and lichenoid drug eruption (46.7% vs. 0.0%, p = 0.002). 12/54 (22.2%) of CADRs patients had positive reaction with saline alone. Among these patients, 4/12 (33.3%) were lichenoid drug reaction, 3/12 (25%) were DRESS, and 2/12 (16.7%) were MP rash. Allopurinol was the drug giving positive patch test only with saline. Conclusion: Appropriate vehicles are essential to obtain the positive drug patch test. Using saline as a vehicle can increase the positive reaction of drug patch test, particularly in lichenoid drug eruption. We recommend the use of saline as another traditional vehicle in drug patch test.