Skin prick test in duplicate: is it necessary?

BACKGROUND: Duplicate skin prick testing has previously been recommended because of reports that accidental negative tests are common. However, duplicate tests also mean an extra allergen load, which may increase the risk of inducing a generalized reaction at the test situation, at least in the youngest infants. OBJECTIVE: To investigate whether the occurrence of both a positive and negative test result is a common feature when performing duplicate skin prick tests and can therefore justify the duplicate method. METHODS: A retrospective analysis of all skin prick tests performed in duplicate at the pediatric clinic at University Hospital in Linköping, Sweden, in 1997. RESULTS: Of 1,087 skin prick tests, 14 resulted in one positive and one negative test, or 1.3%. The corresponding figure in the youngest age group, (ie, <2 years of age) was 3 of 340 (0.9%). CONCLUSIONS: Considering the risk of inducing a summation of the reactions, and thereby a generalized allergic reaction, when applying an extra allergen load on the limited surface of the small arm, we conclude that the results of this study justify using single prick test, at least in the youngest age group and probably when testing children of all ages.

Skin prick tests may give generalized allergic reactions in infants.

BACKGROUND: Skin prick testing, a widely used method of studying sensitization, is usually considered quick, pedagogic, and relatively inexpensive. Previous studies have shown very few negative reactions and no fatalities. In contrast, both anaphylaxis and death have been reported as a result of intracutaneous tests. OBJECTIVE: To examine detailed case studies of generalized allergic reactions in connection with skin prick testing in order to identify possible risk factors and thereby increase the safety of the test procedure. METHOD: A retrospective study of medical records of six cases with generalized allergic reaction occurring during the study period 1996-1998 at the Pediatric Clinic, University Hospital of Linköping, Sweden. Data about the total number of children tested during the period were collected from the clinic's database. RESULTS: All six cases with generalized reactions were infants <6 months who showed positive skin prick tests to fresh food specimen. Other common features were active eczema and a family history of allergic disease. All infants received prompt treatment and recovered well. The overall rate of generalized reactions was 521 per 100,000 tested children. In the age group <6 months, the corresponding figure was 6,522 per 100,000. CONCLUSION: The risk of generalized reactions after skin prick test with fresh food specimens in young children ought to be acknowledged and should lead to increased precautions when performing the test.