Patch testing in drug cutaneous adverse reactions: value of the extemporaneous preparations

Background Patch testing (PT) is a part of tools used for the etiological diagnosis of a cutaneous adverse reaction (CADR). Positivity of PT is observed in above 30 to 50 % of explored cases. Recommended procedure is based on dilution in petroleum or in water at 30 % for the finished product or at 10 % for the active ingredient. Chemotechnique laboratory supplies, in the form of ready for use syringes, around 30 active ingredients. Other medicines must be thus prepared by a hospital pharmacy, according to the strict protocol. Thus, preparations are not available in all the test centers and some patients can not be explored. We led a forward-looking study comparing the extemporaneous tests, easily practicable, compared with the recommended procedures. Patients and methods The programmed tests were performed at the same time with Chemotechnique products or pharmaceutical preparations and with tablets brought by the patients, crushed manually with a pestle in order to transform in powder and then mixed in petroleum. The used chambers were Q or IQ chambers ( Chemotechnique ) and the readings realized at 48 and 96 hours.