DETECTION AND CLINICAL RELEVANCE OF A TYPE-I ALLERGY WITH OCCUPATIONAL EXPOSURE TO HEXAHYDROPHTHALIC ANHYDRIDE AND METHYLTETRAHYDROPHTHALICANHYDRIDE

Hexahydrophthalic anhydride (HHPA) and methyltetrahydrophthalic anhydr ide (MTHPA) belong to the group of the acid anhydrides and, among othe r applications, are used in the production of epoxy resins. These subs tances are known as potent low-molecular allergens and induce predomin antly type I allergies according to Coombs and Gell. We examined 110 e mployees exposed to HHPA and MTHPA. With all of them a RAST was carrie d out with the commercially available conjugates of phthalic anhydride (PA) and a skin prick test with 1% and 5% acetonic solutions of PA. I n 109 of these sera a radio allergo sorbent test (RAST) was carried ou t with the not commercially available conjugates of HHPA and of MTHPA. With complaints connected with the workplace the working materials us ed (HHPA, MTHPA) were also checked by means of the skin prick test. Wi th at least one positive immunological finding (in the RAST and/or ski n prick test) in connection with complaints at the workplace, we perfo rmed a workplace-related inhalation test under experimental conditions . Specific IgE against acid anhydrides was detected in a total of 17 ( 15.4%) persons. In the challenge test, six (5.4%) sensitisations were shown to be clinically relevant. On inclusion of borderline positive f indings with PA conjugates the PAST produced three false negative and one false positive finding compared with a RAST with HHPA and MTHPA co njugates. With the conjugates of trimellitic anhydride, in no case cou ld specific IgE be detected. The skin prick test led, in comparison wi th the RAST, to three false positive and three false negative findings . With all clinically relevant sensitisations the skin prick test was regarded as positive. RASTs with conjugates of PA and skin prick tests with native acid anhydrides can, according to our investigations, val idly ascertain workplace-related sensitisations to HHPA and MTHPA.