D2.252 - Confirmation of selectivity pattern to Non-Steroidal Anti-inflammatory Drugs: a retrospective study in a Central Hospital

Non-steroidal anti-inflammatory drugs (NSAIDs) are a leading cause of drug hypersensitivity reactions and accurate diagnosis is important to distinguish between cross-reactive phenotypes and selective reactions Although skin tests are commonly used in the diagnostic work-up to distinguish between phenotypes, their sensitivity and specificity are not yet fully standardized.

This study aims to evaluate patients with a clinical history of selective NSAID reaction using skin test results (prick and intradermal - IDT) and drug provocation test (DPT) with Acetylsalicylate acid (ASA) to confirm or exclude IgE-mediated reactions.

A retrospective study was conducted at a central hospital in Coimbra, Portugal, from August 2022 until December 2024.

Data were collected and analyzed from patient records, including demographic characteristics, clinical history, skin test results with the culprit drug, and DPT with ASA outcomes.

Patients with a selective clinical history, suggesting hypersensitivity to a specific NSAID were included: Metamizole (n=25), Diclofenac (n=2) and Paracetamol (n=3).

A total of 30 patients (median age of 52 years; range 21-79), predominantly female (76.7%) were enrolled.

Of de prick tests and IDT performed, 18 (60%) were positive, 16 for Metamizole, 1 for Diclofenac, and 1 for Paracetamol.

DPT with ASA were performed only in 5 patients.

1. Three patients with a positive IDT had a negative DPT with ASA;
2. One patient with a negative IDT reacted positively to DPT with ASA;
3. One patient with a positive IDT for Diclofenac also had a positive DPT with ASA.

A summary of the results is provided in Table 1 and 2.

The results supported the reliability of skin tests and its concordance with DPT with ASA, confirming a selective hypersensitivity and supporting an IgE-mediated mechanism in patients 1, 2 and 5 and confirming a non-IgE-mediated mechanism in a patient 3. The sensitivity of the IDT was 100%, while its specificity was 50%.

However, the results of patient 4 raise questions about test reliability and highlights the need for further validation.

These findings suggest that skin tests can be a useful tool for identifying potential IgE-mediated reactions, but DPT remains the cornerstone for confirming selective hypersensitivity and guiding management.