POSSIBILITIES FOR DIAGNOSIS OF DRUG ALLERGIES

Drug allergies can be subclassified into three subgroups, which differ in their pathophysiology and require different diagnostic steps: (1.) classical drug allergies, which are directed to the drug itself, a re active compound of the drug, or some contamination of it; (2.) pseudoa llergic reactions, which are caused by non-immune mediated degranulati on of mast cells and basophils, and (3.) autoimmune reactions, in whic h the drug elicits an immune reaction to autologous structures. A very detailed (criminalistic) history has the highest priority for clarifi cation of a suspected drug allergy. In addition, skin tests, serologic al tests and the lymphocyte transformation test may be useful. It is n ecessary to differentiate between tests which imitate the drug elicite d allergic reaction (i.e. Coombs test in drug induced hemolytic anemia ) and tests which only indicate sensitization. The detection of IgG an tibodies to drugs bound to various carriers (nitrocellulose, sepharose ) is controversial and the meaning of a positive result.is unclear. Th erefore, this test cannot be recommended for the routine diagnosis of drug allergy. Special emphasis is placed on the value of the lymphocyt e tranformation test, which is more often positive than other test pro cedures and may sometimes strengthen the suspicion that a disease may be caused by a drug. Nevertheless, this test requires cautious interpr etation as it may be falsely positive as well as falsely negative.