1The first two authors contributed equally to the work.
Influence of total serum IgE levels on the in vitro detection of β-lactams-specific IgE antibodies
Article first published online: 7 APR 2009
© 2009 Blackwell Publishing Ltd
Clinical & Experimental Allergy
Volume 39, Issue 6, pages 838–844, June 2009
How to Cite
Vultaggio, A., Matucci, A., Virgili, G., Rossi, O., Filì, L., Parronchi, P., Romagnani, S. and Maggi, E. (2009), Influence of total serum IgE levels on the in vitro detection of β-lactams-specific IgE antibodies. Clinical & Experimental Allergy, 39: 838–844. doi: 10.1111/j.1365-2222.2009.03219.x
- Issue published online: 11 MAY 2009
- Article first published online: 7 APR 2009
- Submitted 2 May 2008; revised 12 January 2009; accepted 13 January 2009
- β-lactam allergy;
- drug reactions;
- in vitro tests;
- total serum IgE antibodies
Background Allergic reactions to β-lactams are a frequent cause of adverse drug reactions; the diagnosis is based on history, clinical examination, skin testing (prick and intradermal) and demonstration of serum-specific IgE antibodies (Abs).
Objective We compared the diagnostic performance of the Phadia CAP system for the detection of IgE to β-lactams carried out using the new test with cut-off limits of 0.10 kUA/L and the old test with cut-off limits of 0.35 kUA/L for positive results; subsequently, we analysed the effect of total serum IgE values and of atopic phenotype on the diagnostic performance of the tests.
Methods The study comprised a total of 34 patients with a history of immediate adverse reactions to β-lactams, which were confirmed by positive skin testing, and 115 control subjects with tolerance to β-lactams over the last year. The Phadia CAP System was used for the determination of serum total and specific IgE Abs towards penicilloyl G (c1), penicilloyl V (c2), ampicilloyl (c5) and amoxicilloyl (c6). The overall diagnostic performance was assessed as a diagnostic odds ratio (DOR).
Results The new test showed a higher sensitivity (85% vs. 44%) than the old test and a lower specificity (54% vs. 80%) but the overall diagnostic performance was poor (DOR 6.78 vs. 3.16, P=0.333) in both tests. The total IgE value influences the DOR of both tests; DOR was better for values under 200 kU/L [DOR=66; 95% confidence interval (CI): 11.3–384.1] or 500 kU/L (DOR=45.7; 95% CI: 5.3–394.4) for the new and old tests, respectively.
Conclusions The reduction in the positive cut off value has not significantly improved the overall diagnostic performance of the β-lactams-specific IgE assay. Because of the influence of serum total IgE on the detection of β-lactam-specific IgE Abs, the combination of both tests is mandatory in the in vitro diagnostic approach of β-lactam allergy.