Value of immunologic tests in cow milk allergy

The aim of this study has been to clarify the immunopathogenesis and diagnosis of cow milk allergy (CMA). Thirty-four children with symptoms suggestive of CMA had a challenge test with cow milk (CM) and an estimation of their immunological response. Nineteen of the 34 children reacted to CM challenge test. We measured serum levels of immunoglobulins G, A, M and E, complement fractions 3 and 4, class specific CM antibodies as well as the numbers of the different lymphocyte subsets and the responses of lymphocytes in whole blood to stimulation by phytohemagglutinin (PHA), concanavalin A (ConA) and beta-lactoglobulin (BLG). Twelve (63%) of the children who reacted had high levels of IgE CM-specific antibodies; they had lower mean levels of serum IgA and lower lymphocyte stimulation indices with BLG and PHA than the rest of the children (37%) who reacted on CM, but were without IgE antibodies. Of these seven children, five gave elevated responses to stimulation with BLG, and in three of six the helper/suppressor lymphocyte ratio rose during the challenge test. Most (10) of 15 children who showed no reaction when challenged with CM at hospital, had earlier had cutaneous symptoms closely related to CM formula feeding. No single laboratory method was sufficient to discriminate between the children who reacted to CM and those who did not. The best combination of tests was measurements of CM-specific IgE and the index of lymphocyte stimulation with BLG. This combination had a sensitivity of 88% and specificity of 67% for predicting a clinical reaction.