Evidence-based allergy diagnostic tests.

Effective management of allergic diseases relies on the ability to make an accurate diagnosis. Although clinicians rely on experience obtained over many years of practice, such experience is anecdotal and unique to the individual using it. The result is a tendency for patients with similar clinical presentations to receive different diagnoses and treatment, depending on which provider they happened to see. The probability that a patient has a particular diagnosis can be determined using a combination of diagnostic tests. To make the best use of tests, it is important to understand their performance characteristics in terms of reproducibility and likelihood ratios. A test that is reproducible but that does not predict the presence of a disease is not helpful, nor is an accurate test that is not reproducible. To improve the reproducibility of diagnostic tests, it is important that proficiency testing be instituted for both skin and in vitro tests so that the coefficient of variance can be determined. This has already been done for the latter and needs to be done for skin tests as well. With use of a combination of history and appropriate diagnostic tests, the probability that a particular diagnosis is present can be increased or decreased sufficiently either to confirm it or to rule it out. As proficiency testing of allergy tests becomes more common and the use of tests becomes more consistent, we believe that patients with allergic diseases will benefit.