Comparison of a new type of skin test (Phazet) with existing skin test methods and the radioallergosorbent test (RAST).

A new skin test method (Phazet) for diagnosis of immediate-type allergic disease was tested in 232 patients attending the Guy's Hospital Allergy Clinic, and compared with conventional skin test methods, using Bencard and Pharmalgen allergen solutions, and with serum IgE antibody tests (RAST). Six allergens (cat, dust mite, Cladosporium, grass pollen birch pollen and plantain pollen) were used, as well as histamine and a negative control. Phazet proved easy to use and was popular with inexperienced operators (medical and dental students). For the majority of allergens there was reasonably good agreement with the different tests, but overall Phazet and RAST produced fewer positive results than the other skin tests methods. In particular, the frequency of positive histamine tests was lower with Phazet (82%) than with Bencard or Pharmalgen (99%), but this discrepancy was lower in the second part of the study when the minimum time for the insertion of the needle (1 sec) was more scrupulously observed. Phazet offers a convenient and practical alternative to conventional 'wet' skin test methods.