In vitro methods for specific IgE detection in cow's milk allergy.

Background: A new method for determining serum specific IgE (IMMULITE 2000 3gAllergy) has recently become available.

Objective: To evaluate the clinical performance of IMMULITE 2000 in the diagnosis of cow's milk allergy compared with that of UniCAP. Additionally, we verified the behavior of both methods at two diagnostic decision points proposed by other authors.

Methods: The study population consisted of 31 children with cow's milk allergy (group A) and a control group of 19 atopic children without food allergy (group B). A blood sample from each child was tested using both methods and the results were compared.

Results: In group A, the values for cow's milk IgE ranged from 0.35 kU/L (the lowest common detection limit) to above 100 kU/L. In group B, the values were less than 1.1 kU/L for IMMULITE 2000 and less than 1.6 kU/L for UniCAP. An agreement of 90% in IgE classes was obtained. Both methods demonstrated exactly the same diagnostic performance (sensitivity: 100%; specificity: 78.9%; negative predictive value: 100%; positive predictive value: 84.6%; efficiency: 90.2%). The evaluation of the two methods at the two different decision points proposed in the literature showed a better positive predictive value with UniCAP, but we obtained equivalent performance with IMMULITE 2000 by choosing higher cutoff values.

Conclusions: We conclude that IMMULITE 2000 is as effective as UniCAP in the diagnosis of cow's milk allergy. Both methods can be used to obtain site-specific decision points that are population, age and disease dependent.