Active surveillance of severe cutaneous adverse reactions: A case‐population approach using a registry and a health care database.

Abstract: Purpose: The “case‐population” design has been proposed for the surveillance of rare events like Stevens‐Johnson syndrome/toxic epidermal necrolysis (SJS/TEN), wherein a registry of cases is combined with sales data from the source population in order to estimate crude odds ratios (ORs). A major drawback of this method is the inability to distinguish between new and non‐new users of drugs, which for the study of hypersensitivity reactions is of utmost importance. Methods: We have explored an approach in which the exposure to the drugs of interest in the source population is inferred from a primary health care database (BIFAP), which helped us to identify drug initiators among all users and additionally adjust for potential confounders. A total of 44 SJS/TEN cases from the Registry and 44 000 controls randomly sampled from BIFAP and matched with cases for index date were included. We estimated the adjusted ORs (AORs) and 95% confidence intervals (CI) of SJS/TEN associated with the new use of 13 drugs (for which we had at least two exposed cases) through a conditional logistic regression model. Results: AORs (95% CI) were estimated for phenytoin, 4618 (434‐49112); cotrimoxazole, 1142 (163‐8015); allopurinol, 160 (36‐709); dexamethasone, 38 (1.33‐1077); ibuprofen, 33 (8.6‐124); lorazepam, 27 (5.8‐124); paracetamol, 13 (2.8‐62); levofloxacine, 12 (1.24‐120); amoxicillin, 6.9 (1.39‐35); pantoprazole, 6.5 (0.10‐420); metamizole, 6.3 (0.69‐57); amoxicillin clavulanic acid, 4.2 (0.53‐34); and omeprazole, 1.34 (0.06‐31). The inclusion of non‐new users dramatically decreased the AORs for all drugs. Conclusions: The case‐population approach using a registry of cases and a primary health care database proved feasible and efficient for the active surveillance of SJS/TEN. [ABSTRACT FROM AUTHOR]