Challenge is not crucial

doi:10.1136/bmj.b3622

Published 7 September 2009, doi:10.1136/bmj.b3622
Cite this as: BMJ 2009;339:b3622

Letters

Cow’s milk allergy in children

Challenge is not crucial

The first 150 words of the full text of this article appear below.

Apps and Beattie state that diagnosis of cow’s milk allergyshould be confirmed by challenge, even in those at risk of severereactions.¹ In practice, such confirmation is rarely done asit can be dangerous, is resource consuming, and is often unnecessarywith a good history, positive test results (skin prick or specificIgE), and improvement with elimination of cow’s milk.²Oral challenge should be reserved for cases with large diagnosticdoubt, and for determining whether a known food allergy hasresolved.

The authors incorrectly imply a significant difference in positivepredictive value between specific IgE and skin prick testing.A positive specific IgE test does not have a positive predictivevalue as high as 90-95%. Specific IgE value may be important.A positive predictive value of 90% refers to specific IgE >2.5kU(A)/l in infants under 12 months.³ The threshold varies indifferent studies: a threshold for milk of . . . [Full text of this article]

Yousuf Karim, consultant immunologist¹, Zoe Adhya, speciality registrar in immunology²

¹ Frimley Park Hospital, Frimley, Surrey GU16 7UJ, ² Royal Surrey County Hospital, Guildford GU2 7XX

yousuf.karim@nhs.net