Abstract
Background:
Skin prick tests (SPT) are widely used both in clinical practice and in research. The standardization
of the allergen extracts is well documented to be crucial for the validity of SPT, whereas less
emphasis has been on reproducibility and the SPT procedure itself.
Objective: To study how the duplicate skin prick test procedure influence the sensitivity and
specificity of the test and to analyse the differences in wheal size in skin prick tests with two
batches of allergen extracts from same vendor.
Methods:
The association between rhinitis and SPT was assessed among 1135 subjects from a general
population sample. SPT was performed twice with 10 common aeroallergens. In a subsample of 90
persons SPT was performed simultaneously with five of the allergens using two different batches
Results:
Thirty percent had at least one positive SPT. Only minor disagreements were seen between the sizes
of two wheals from the same batch. A second SPT with the same batch did not change the
association between rhinitis and sensitization. When performing SPT with two different batches
disagreement was observed in 2 % (Birch) to 11% (Dog) of the subjects.
Conclusions:
Performing SPT twice with the same allergen batch does not enhance the validity of the test, and
duplicate testing cannot be recommended. Considerable difference in SPT response was observed
when using different batches from the same vendor. Thus, inter batch differences in allergen
extracts might be a source of variability.
- © 2014 ERS