The shape of and applied weight on skin prick lancets critically affect the wheal size in the skin prick test

The global application of the skin prick test (SPT) is attributed to the low costs, easy execution, and in vivo approach. Still, the healthcare professionals’ technique and the lancet shape may challenge the standardization of the method. Thus, we investigated the influence of the shape of the lancet and the applied weight on the wheal size of SPT. Two allergic and one non-allergic individual were tested with allergens (Dermatophagoides pteronyssinus and Phleum pratense) and histamine solution (positive control), respectively. Horizontally (HS) and diagonally (DS) shouldered lancets with the same tip length (1 mm) were tested under two different conditions: either 60 g or 120 g weight pressure. The wheal size induced by the 4 different combinations was measured. The higher-weight device (120 g) induced a significantly larger and less variable wheal response with the tested allergens and histamine. However, the shape of the lancet affected the wheal size more than the applied weight. The least variable response was measured to histamine for the horizontal-shouldered lancet combined with the higher weight, whereas the same lancet with the lower weight resulted in a significant number of false negative results.