Predictive value of skin prick tests and radioallergosorbent tests for clinical allergy to dogs and cats.

The predictive value and post-test probability of disease were compared for skin prick tests and radioallergosorbent tests (RASTs) in 168 children suspected of clinical allergy to dogs and cats. The skin tests included negative and positive (histamine) controls. The results of RASTs with the same allergen extracts were expressed in relation to the results with allergen-specific pooled reference serum. All the tests were performed blind. The predictive values of positive test results were comparable and low (53% to 76%), whereas the predictive values of negative test results were comparable and high (88% to 95%). The post-test probability of clinical allergy to dog or cat allergen, based on the prevalence rates in the referral population (15.1% and 22.5% respectively), increased to between 46% and 67% for positive test results and decreased to between 4% and 8% for negative results, which suggests that the primary role of skin prick tests and RASTs is in eliminating the diagnosis of clinical allergy.