THE PHADIATOP(R) TEST COMPARED WITH RAST, WITH THE CAP SYSTEM - PROPOSAL FOR A 3RD PHADIATOP OUTCOME - INCONCLUSIVE

In 19 general practices, blood samples were obtained from 361 patients aged 12 years or older with chronic nasal symptoms. The Phadiatop tes t and a panel of RASTs to common inhalant allergens were performed on all sera with the recently introduced Pharmacia CAP system. The PAST p anel was accepted as the standard. The sensitivity of the Phadiatop wa s 94% (95 % confidence interval (CI): 89-97 %), the specificity 98 % ( 95 % CI: 95-99%), the positive predictive value 97% (95% CI: 94-99%), and the negative predictive value 95 % (95 % CI: 91-98 %). It is notew orthy that these values are very similar to those found in hospital ou tpatient departments. It was possible to reduce further the small perc entage of false outcomes by replacing the cutoff point of the Phadiato p ratio of 1.00 by the two cutoff points 0.75 and 1.15. This resulted in three possible outcomes: a highly predictive positive outcome, a hi ghly predictive negative outcome, and an ''inconclusive'' outcome. Alt ernatively, the cutoff point of 1.00 may be maintained while attaching the annotation ''borderline'' to all positive or negative Phadiatop o utcomes where the Phadiatop ratio is between 0.75 and 1.15. By this si mple method, physicians are alerted to the possibility of a false outc ome; on the basis of the case history and other clinical findings, the y can then decide whether further testing should be done.