D3.91 - Safety of Skin Prick Tests: more than 30 years of spontaneous data from real practice

The skin prick test (SPT) is the first-line approach for the diagnosis of allergy because of its accuracy and safety, in addition to the ease of use and low cost. Allergic systemic adverse reactions (ADRs) to SPT have been reported and appear to be more frequent with certain allergens (such as food, latex, drug, hymenoptera venom), multiple testing in the same individual, younger age and active eczema. Rare occasional life-threatening reactions have been documented, suggesting a remote risk associated with SPT, particularly in patients with a history of anaphylaxis. Therefore, proper emergency management should always be considered. Although generally safe, there is limited information available regarding SPT extracts in routine practice.

The Lofarma internal pharmacovigilance database was reviewed to extract data collected from the post-marketing period between 1988 and 2020, to calculate the rate of ADRs related to hydroglyceric extracts of inhalant and food allergens, as well as positive and negative control solutions. Standardized extracts of epidemiologically relevant allergens are titrated to 100 Diagnostic Biological Units (DBU)/ml, corresponding to an allergenic activity (10 HEP) that induces a positive skin reaction comparable to that obtained with histamine 10 mg/ml. Extracts of allergens with minor epidemiological significance are expressed as weight/volume percentage. Each 3.5 ml bottle of allergenic solution can test approximately 70 patients for a single allergen. Pharmacovigilance surveillance for diagnostic agents typically includes reports of misuse, quality issues and low performance from users.

No ADRs were found associated with the use of SPT on over 1,300,000 bottles sold. Eight cases of spontaneous reporting were received for abnormal skin reactivity or apparent discrepancies between SPT results and clinical history, other SPTs or IgE in vitro tests: 4 cases of false negative reaction and 1 case of lower-than-expected skin reactivity; 2 cases of false positive reaction, and 1 case of higher-than-expected skin reactivity. No episodes of anaphylaxis or use of adrenaline during or after SPT procedure were reported.

The safety of the SPT procedure using Lofarma allergenic extracts from various sources is evident through more than 30 years of clinical use. Very limited reports of low performance were identified, confirming that SPT remains an accurate method for diagnosing allergies.