• CAST;
  • Cys-LT;
  • drug allergy;
  • histamine release

Background: The diagnosis of allergic reactions to drugs is difficult. Most skin tests are not standardized, and in vitro tests are needed to avoid provocation tests. Cross-linking of IgE on basophils is known to cause the release of both cysteinyl leukotriene (Cys-LT) and histamine. We aimed to evaluate the diagnostic utility (sensitivity, specificity, and efficiency) of measurement of sulfidoleukotrienes in drug allergy.

Methods: We performed a prospective study in 55 patients with proven immediate adverse reactions to drugs (30 to β-lactams, six to acetaminophen, and 19 to aspirin) and 64 drug-exposed nonallergic controls. Positive diagnosis was established by history, skin tests, and, if needed, oral provocation tests. Cys-LT release was determined after drug-allergen stimulation by the cellular antigen stimulation test (CAST®) technique. Histamine release was also assessed on the same samples by enzyme immunoassay. Spontaneous and anti-FcεRIα-induced mediator release was also studied in all subjects. Sensitivity, specificity, and efficiency were calculated.

Results: Net Cys-LT release was over the maximal threshold given by the manufacturer in 19/55 patients and in 9/64 controls. Net histamine release was over 5% of total histamine content in 28/55 patients and 34/64 controls. The efficiency of both tests was low.

Conclusions: Thus, in most cases, the in vitro Cys-LT test has little or no diagnostic utility and is not superior to histamine release.