Background: Improperly performed skin prick tests (SPT) can lead to wrong allergy diagnosis and incorrect treatment. To overcome false-positive results it is recommended to change the puncture device between each test, although very few studies have examined the real drawbacks (false-positives) and advantages (time and cost savings) of using only one device.
Methods: Two groups of 20 patients with rhinitis or asthma, sensitized to either house-dust mites or grass pollens, had successive serial SPT to 9% codeine phosphate and the relevant allergen using the same needle or lancet, wiped between each test.
Results: With both the needle and the lancet, there were 12.5–67.5% false-positive results using the house-dust mite or grass pollen allergen extracts, respectively. There were no false-positive results with the 9% codeine phosphate.
Conclusions: Our study shows that this technique is not reliable as it provoked an unacceptable number of false-positive results.