In vitro and skin testing for allergy: comparable clinical utility and costs

Controversy exists concerning the appropriate use of skin testing and in vitro testing for the diagnosis of allergy, particularly inhalant allergy. Earlier comparisons of skin testing and in vitro testing concluded that skin testing had superior accuracy at lower expense. In light of new developments with in vitro allergy testing, however, this issue should be reconsidered. A review of the recent scientific literature indicates that in vitro and skin testing are highly correlated. However, without the existence of an independent gold standard for inhalant allergy, it is not possible to determine which test is more accurate. The accuracy of either test can be compromised if conducted using different protocols or having insufficient quality control. Given their respective trajectories for technological advancement, quantification, and quality control, in vitro testing may offer the more standardized approach. Although the cost per test of in vitro testing remains greater than that of skin testing, the per-patient costs of the two modalities appear to be comparable, given the greater number of allergens typically used in skin testing. In summary, both skin testing and in vitro testing are acceptable as frontline diagnostic tools.